hension, tearing and division of the flesh by means of the characteristic teeth.

In the Edentata, on the other hand, the cranium of the great ant-eater exhibits a jugal arch which is the extreme opposite of that which has been thus partially described. Here, it is very incomplete, consisting of a short styliform process given off by a very rudimentary jugal, and of an extremely small tuberous zygomatic process from the squamosal, no union being formed between the two. There is no postorbital process of the frontal, and no separation between the orbital and temporal fossæ. Under these circumstances, the muscular development concerned in the preparation of the food is very feeble, correlated as it is with the entire absence of teeth and any necessity for mastication.

Between these two extreme modifications, there are many intermediate forms of this arch, as will become evident as we study them in the different orders of the Mammalia.

In the PRIMATES the arch is composed of two bones, the squamosal and malar, which are joined by a serrated suture which inclines downwards and backwards; the amount of inclination being modified in the various groups of this order. The strength and curvature of the arch also widely vary, as does also the extent to which the various crests and ridges for muscular attachment are developed. In man, the arch is generally slender, slightly curved in its horizontal axis, and presents a very moderate convexity upwards in its vertical curvature. Owing to the slight horizontal curvature outwards, the temporal fossa is relatively shallow, consequently allowing but little development of the temporal muscle. This condition, however, is subject to modifications in the various races of The maximum breadth of the cranium is at the jugal arches, and it is at these points that craniologists now take the bizygomatic diameter of the face.

man.

Humphrey, in his Human Skeleton, in speaking of this arch, says: "The upper surface of its root forms a smooth channel for play of the temporal muscle. In the negro the greater width of this channel throws out the zygoma into stronger relief, and added to the flatness of the squamosal portion, affords more space for the temporal muscle." This general statement is not confirmed by any cranial measurements, neither does Mr. Humphrey state what he means by a negro. Probably he intended, as in common parlance, to designate the African, although this designation is ambiguous, as it is well known that the crania of the different tribes of Africa differ very essentially in their general formation, as well as in their special cranial measurements.

Although the cephalic measurements of Broca, Topinard, and others allow a slight increase in the horizontal curvature of the arch in certain instances, which signify a greater development of the temporal muscle, as well as a more extended surface for the attachment of the masseter, yet, as Topinard remarks, in speaking of the bizygomatic diameter, "This measurement by itself often presents difficulties, purely accidental and

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[Slade. local, and entirely apart from the general type. Thus, in every race, cases occur in which the zygomatic process of the squamosal, instead of joining directly with the malar, bends outwards and then resumes the general characteristic direction of the arch, whether this be straight or gently curved. The greatest width under the circumstances falls upon the summit of the bend, which causes the measurement to be unduly augmented."

As a result of the measurements taken upon the crania of the Africans in the collection of the Peabody Museum, and of the Harvard medical school, there was a slight increase in the bizygomatic breadth over those of other mixed European skulls. But no dependence should be put in such measurements, for although in one collection the crania were classified in general as African, nothing was known of their history, and still less of those with which they were compared.

Tables given by Topinard, Flower, and others, of the bizygomatic breadth compared with the total length of the face, apparently do not sup port the statement of Mr. Humphrey. A more satisfactory method of ascertaining the truth of the point in question would be to obtain by measurement the actual width of the groove in the upper surface of the posterior root of the zygoma, of the African skull and compare this with that of other races. This can be properly effected by taking first the bizygomatic breadth and then the bisquamosal at the most prominent point on the line of suture between the squamosal and alisphenoid; the difference between the measurements would give the breadth of groove.

Cuvier reminds us that the size of the temporal fossa and its muscle have close relation with the age of the animal. In the young, the brain and its case are developed, but the jaws are small, and the forces which move them are wanting in energy. But with age these last are developed, while the intellectual powers constantly diminish. In civilized man, the equilibrium is maintained between the growth of the brain-case, the intellectual powers and the masticatory organs. Can any relation, however remote, be traced between the developed masticatory powers of the uncivilized negro, and the flattened squamosal of his brain case as described by Mr. Humphrey ?

The Anthropomorpha have strong jugal arches, longer than in man, and presenting marked horizontal and vertical curvatures. Although, strictly speaking, it is composed of only two bones--the zygomatic process of the squamosal and the jugal, this last rests upon a process of the maxilla so much developed, that in many cases it might be rightfully con sidered as entering into the formation of the arch. The suture which joins the squamosal and jugal is long and serrated, its great inclination downwards and backwards vastly increasing the strength of the parts as also the power of resistance.

In the gorilla, the arch is relatively broader and more developed than in the other higher apes. The process of the squamosal presents a sudden vertical convexity upon its upper border, at a point corresponding to the

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[March 15, junction of the anterior transverse root, the remaining portion of the arch being nearly of the same width. The breadth of the channel for the play of the temporal muscle is proportionally large. The entire structure of the arch, especially in its horizontal-vertical curvatures, exhibits enormous strength. In the adult male all the cranial ridges attain their maximum size, thus presenting a largely increased surface for the origin of the temporal muscle, while the relative greater breadth of the ascending ramus of the mandible and the increased width of the pterygoid fossæ are correlated with a corresponding development of the masseter and pterygoid. The long and massive canines have reference to the powerful action of the last named muscles, while their use has a sexual relation. The glenoid cavity is transversely broader than in man, and more shallow, its anterior boundary, formed by the anterior root of the zygoma, being scarcely developed, thus allowing greater freedom for the antero-posterior movement of the articulation of the mandible.

In comparing the skull of the male gorilla with that of man, we shall find that the arch of the former is not only vastly stronger, but the bones present a different form and proportions. The squamosal is as long and vertically as wide as the malar portion of the arch, while its upper border rises into an angular form, constituting a very marked convexity, no trace of which is to be seen in man. In the latter the jugal portion of the arch decreases in depth after leaving the body of the bone, whereas in the gorilla it continues of the same depth and is relatively longer.

In the orang, the horizontal curvature of the arch is greatly produced, and strongly developed at the portion corresponding to the malar-squamosal suture. Its inferior border is flattened and thickened. The vertical curvature, however, is not so great, while the channel for the temporal muscle is relatively wider than it is in the gorilla. The crests and ridges of the cranium, especially in the male, express the great energy of this muscle, although the general outline of the arch is far less massive than in the latter ape.

The jugal arch of the chimpanzee presents much resemblance to that of man, being narrow, and with slight curvature, either horizontal or vertical. The malar is anteriorly flatter, and its orbital process is longer and narrower at its base. The extent of surface for the development of the temporal muscle is greater than in man, and the width of the channel relatively increased.

The slight modifications observed in the arch of the gibbons, exhibit a distinct tendency to those shown in the lower types of the Simiadæ. In the old-world monkeys, the arch takes on a sigmoidal curvature, thus presenting upon its superior border, a slight convexity behind and a corresponding concavity anteriorly. The extent of this curvature varies in the different groups. In the new-world monkeys, the postglenoid process of the squamosal is largely increased, while the remarkable extent of the ascending portion of the ramus, both vertical and antero-posterior, has

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[Slade.

reference in the howlers to the great development of the vocal organs, rather than to any unusual energy of the masticatory muscles.

In the Lemuroidea, the family of the common lemurs have an arch which in most cases is nearly straight, narrow, long, and distinguished by a malar-squamosal suture, which is almost horizontal in direction, the amount of the overlapping of the jugal by the lengthened process of the squamosal being exceptional, while in some cases the jugal is partially underlapped by a process of the maxillary.

As regards the Carnivora, the general characteristics presented by the arch and the adjacent regions have already been considered, when taking that of the tiger as a typical illustration of their morphology. The order of the Carnivora is divided into two suborders, the true or fissiped and the pinniped (the latter being organized mainly for an aquatic life). The true Carnivora may be classified under three sections-Eluroidea, Arctoidea and Cynoidea. The arch in the families comprehended under the first of these sections presents no modifications specially different from those offered by the Felidæ, unless we may except the Hyænidæ, in which the jugal arch is extremely wide and strong and the horizontal curvature very great. The postorbital of both frontal and jugal are largely developed, approximating each other, while the sagittal crest is high, giving large attachment to the very powerful muscle of the temporal. The ascending rami of the mandible present the corresponding extent of surface for muscular attachments. In the section Arctoidea, the family Ursidae present an arch which is longer, and of which the horizontal curvature is greater than that of the Felida, while the jugal-squamosal suture is more oblique, and the entire bridge much less developed. In the Mustelidæ, the upward vertical curvature is large, but the entire arch is relatively slender.

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[March 15,

those of the Arctoidea, but exhibiting less strength than those of the Eluroidea.

The suborder Pinnipedia is easily separated into three families-the Otaridæ, the Trichecida and the Phocida. The first of these bear genetic relationship to the Ursidae in many of the cranial characters. The arch is composed, as in the Fissipedia, of three bones. Of these, the jugal presents a wide backward progressing process, which divides into a short upper and a long lower one, receiving and supporting the extended process of the squamosal, as in a mortise.

The postorbital processes are well developed. A more or less distinctly marked sagittal crest exists with an extended surface for muscular attachment. The coronoid surface of the ascending ramus is wide, but not produced above the level of the arch.

In the Trichecida, of which Trichecus is the single genus, the maxilla enters largely into the formation of the arch, the jugal is shorter and broader than it is in the other families, and nearly quadrangular, sending up a prolonged postorbital process from its superior border, while pos teriorly its inferior border underlies the process of the squamosal. The condylar surface of the mandible points backwards, while those of the rounded coronoids are scarcely lifted above the dental series.

In the Phocidæ, the composition of the arch does not differ essentially from that of the Otarida, although it is relatively much weaker. There are no postorbital processes, and the sagittal crest is less distinctly marked. The angle of the mandible is not inflected.

The Chiroptera are divisible into the suborders Magachiroptera and Microchiroptera. The family Pteropodidæ includes all the characters of the first of these suborders. In Pteropus, the arch is long and relatively slender, and composed of three bones, of which the jugal is splint-like, adhering to the outer and under surface of both the squamosal and maxilla, which meet above it and form the span.

The postorbitals of the frontal and jugal not unfrequently meet, and thus complete the bony orbit. There are strongly developed crests, both occipital and sagittal. The coronoid surface of the mandible is fitted for large muscular attachments, being high, broad and recurved. The angle is flattened and rounded, presenting an extended surface. Of the six families into which the suborder Microchiroptera is divided, the Vespertilionidæ may be taken as the typical representatives. The arch is slender and complete throughout the entire group, except in some of the Phylostomidæ, in whom it is entirely wanting.

When present, the horizontal curvature is large, and the vertical also considerable, the convexity being upwards. In its conformation, it is similar to that of the Pteropodidae. The orbit is incomplete, the temporal fossæ are relatively large. The parietal crest is but slightly developed. The mandible is stout and high at the symphysis. The ascending ramus is compressed, and bears a coronoid process which is strongly indented for muscular attachment. Immediately below the condyle, is a backward