shown Dr. Packard that his definition and limitation of that group is extremely faulty. Dr. Packard's new family, Gampsonychida, is apparently valid, and belongs, where he has placed it, among the Schizopoda. In his paper on this group we observe that he regards his Syncarida as an ancestor of the schizopods. It is not easy to see how our knowledge of crustacean embryology supports such a view, for in development a schizopodal condition usually precedes the single-branched appendage. So far as the plates show, there is nothing except the telson to separate the family Anthracaridæ from the true Caridea, or to indicate that it differs from any existing group. The telson, however, is greatly different, approaching most closely in its appearance to that of the existing genus Euceramus of Stimp

son.

The paper on the "Xiphosura of the Carboniferous" is the best of the series, containing as it does, in addition to the description of new forms, a résumé of our previous knowledge. It would seem, however, that the reference of Cyclus americanus to the genus Cyclus is hardly warranted. Except in the possession of a circular outline, Cyclus and the form in question have little in common. With regard to the other forms described or redescribed by Dr. Packard, but little needs to be said. The relegation of Euproops into synonymy seems warranted, but the sub-order Synziphosuridæ, with its four new families, should have, at most, but family rank. For the Merostomata and Trilobites Dr. Packard proposes a class, Podostomata, the definition of which could be very seriously criticised. The most prominent point, however, to be mentioned is that Dr. Packard, in this new group, actually renames one of his own groups, which in turn was well enough named before. A slight variation in the limits of the Gigantostraca of Haeckel and Dohrn makes this group synonymous with the later Palæocarida of Packard, while, so far as we can see, Packard's Palæocarida and Podostomata are absolutely identical.

In closing this review, we may call attention to a tendency on the part of our author to rename things already well named, and his pages fairly bristle with "arthrosome," "bænopod," urosome,' cephalula," and the like,-all synonymous with previously-coined and widely-used terms. The learning of this new nomenclature, in order to read intelligently one of Dr. Packard's later productions, is, as suggested by Col. Theodore Lyman in another connection, extremely like sawdust-swallowing, neither palatable nor nutritious.

Thomas on Mammalian Dentition.—The reader who expects On the Homologies and Succession of the Teeth in the Dasyurida, with an attempt to trace the History of the Evolution of Mammalian Teeth in General. By Oldfield Thomas (British Museum). Philos. Transac. Royal Society, 1887, p. 443.

to find in this memoir a history of the evolution of Mammalian dentition will be disappointed, for it embraces only a history of the evolution of the milk-dentition and the nature of dental succession. To this end the author has written a very useful paper, and illustrates it with numerous instructive diagrams and figures. He first describes the dentition of the Dasyuridæ, and shows how the third, or, as he calls it, the fourth, superior premolar has disappeared, leaving but three in the genera Dasyurus and Sarcophilus. As Mr. Thomas calls the fourth superior premolar in the Marsupialia a true molar, he finds only two left in the genera named, and, believing that four premolars must be accounted for, he endeavors to show that another premolar has been lost in those genera. He concludes that the second is the missing one, and reaches this opinion by finding on one side of a single skull of Phascogale dorsalis a supernumerary tooth between the first and second premolars. In our opinion, this supernumerary tooth, if anything more than an abnormality, can only represent a former tooth of a series of five. Similar teeth have been observed in the inferior series in Miacis edax Leidy, and Coryphodon latidens Cope. It is quite unnecessary to complete the number of four premolars, since four are accounted for, after the replacement of the third, which is wanting in Dasyurus. The fourth is of molariform structure, and has been therefore regarded as a true molar by Flower and Thomas. The fact that it is in the genus Trïïsodon and probably others (as Mioclænus, where there are four inferior premolars), shed and succeeded by a premolariform permanent tooth, is conclusive as to the homology, as I have pointed out.1 Mr. Thomas finds my description of this genus "incomplete and confusing," and the reason why he does so is apparent from the above description of his views.

Mr. Thomas believes that the milk-dentition is not a remnant of a primitive succession derived from Reptilian ancestors, but holds, with Professor Flower, that it is a superaddition gradually introduced in the evolution of the Mammalia. The lack of milkteeth other than the third premolar (or its homologue), from the Jurassic Mammalia, strongly supports this view. The fact that the temporary fourth premolar is in most placental Mammalia more complex than its permanent successor, is also in favor of this view, so far as it goes; and the fact that this complex tooth is permanent in the implacentals still further supports the opinion of Flower. On this view it appears that the placental has added to the implacental milk-dentition one tooth posteriorly and two anteriorly. It then looks as if the deciduous dentition consisted of primitive teeth retarded in their protrusion by more precocious ones. This is essentially Mr. Thomas's explanation,—which approximates that of Baume, who, however, differs in the method

1 Final Report U. S. Geol. Survey Terrs., iii. Bk. i. p. 270, 1885.

of statement. Baume1 regards the milk-dentition as expelled by the crowding of the germs of the permanent teeth in the jaws, and so caused to protrude earlier. The opinion of Thomas is preferable, since teeth of accelerated growth will certainly retard or repress germs of slower growth, and not weaker germs expel stronger germs, as Baume's theory requires. Moreover, milkteeth appear at normal age for teeth, while the permanent ones are late. Mr. Thomas finds difficulty in accounting for such precocity and such crowding. Mechanical evolution furnishes the explanation. It is due to the shortening of the jaws; and this is a consequence of the development of the canine teeth from use, and the consequent forward movement of the masseter muscle and its insertions.2

It may be observed that the unnecessary terms Prototheria and Eutheria, which are generally ascribed to Professor Huxley in England, were really introduced by Professor Gill.3-E. D. Cope.

Jordan's Science Sketches.4-When Dr. Jordan undertakes the description of a fish his language is the language of science; when he turns his pen to the popularization of scientific subjects he still retains his former conciseness, but at the same time he manages to introduce many epigrammatic sentences and no little quiet humor, the latter the more enjoyable from the thoroughly natural manner in which it is used. His recent book, "Scientific Sketches," is made up of a series of articles, lectures, and addresses, most of which have appeared separately before, but which are welcome in permanent shape. Four of the sketches relate to fishes, dealing with the life of a salmon, the habits of the "John Darters," a sketch of the salmon family, and the dispersion of fresh-water fishes. Three are biographical sketches, the subjects being Rafinesque, Poey, and Darwin. The "Story of a Stone" is a bit of geological history for young readers; the "Ascent of the Matterhorn" is the least scientific, the "Nomenclature of Birds" the least popular, of the essays. The last essay in the volume, "The Evolution of the College Curriculum," is by far the most valuable, but to be fully appreciated it should be read in the light of the experiment in collegiate instruction which is being tried at the Indiana University, of which Dr. Jordan is the president. Dr. Jordan's idea is that a college should provide both the facilities for a general culture and also for detailed study; that, while teaching the elements of

I only know this from Schlosser's description, Morphologishes Jahrbuch, 1886,

P. 110.

2

* See Cope, The Mechanical Origin of the Sectorial Dentition, Proceeds. Amer. Assoc. Adv. Sci., 1887.

3 Arrangement of the Families of Mammals, Smithsonian Contributions to Knowledge, 1872, pp. v., vi.

Science Sketches. By David Starr Jordan. Chicago: A. C. McClurg & Co.

several subjects, it should give each student a thorough drill in some one branch. The scheme has been thoroughly worked out on paper, but time alone can tell how it results. It must be said, however, that it has amply satisfied its advocates during the two years that it has been tried.

Hepatica Americanæ.-The first twenty numbers (Decades I. and II.) of this distribution, by Dr. L. F. Underwood and O. F. Cook, were received in the latter part of November. The species represented are as follows, viz.: I. Riccia natans L.; 2. Marchantia polymorpha L.; 3. Conocephalus conicus (L.) Dum.; 4. Anthoceros lævis L.; 5. Blasia pusilla L.; 6. Steetzia lyellüi Lehm.; 7. Frullania grayana Mont.; 8. Lejeunia serpyllifolia Lib., var. Americana Lindb.; 9. Madotheca porella (Dicks.) Nees.; 10. Radula complanata (L.) Dum.; 11. Ptilidium ciliare (L.) Nees.; 12. Bazzania trilobata (L.) B. Gr.; 13. Trichocolea tomentella (Ehr.) Dum.; 14. Lepidozia reptans (L.) Dum.; 15. Kantia trichomanis (L.) B. Gr.; 16. Geocalyx graveolens (Schrad.) Nees.; 17. Cephalozia curvifolia (Dicks.) Dum.; 18. Jungermania schraderi Mart.; 19. Scapania nemorosa (L.) Dum.; 20. Plagiochila porellioides Lindenb.

The specimens are carefully selected, and are neatly labelled. As will be seen, they represent the four orders of Liverworts, as well as all the larger genera. The set is well worth the price asked for it ($1.25). It may be obtained of Dr. Underwood, at Syracuse, N. Y. Teachers of botany will find this set a valuable one for their beginning classes.—Charles E. Bessey.

GENERAL NOTES.

GEOLOGY AND PALEONTOLOGY.

The Sonora Earthquake of May 3, 1887.-On the afternoon of May 3, 1887, at 2.12 Pacific time (=120° W. of Greenwich), the first of a series of earthquake movements was felt in the State of Sonora and the adjacent parts of Mexico and the United States, over an area extending from El Paso in Texas on the east to the river Colorado and the Gulf of California on the west, and from the State of Sinaloa on the south as far north as Albuquerque in New Mexico; the extremes in both directions being over five hundred miles. It was the fortune of the writers to be at the time at the great copper-mining camp of Bisbee in Arizona, in a narrow gorge of the Mule Pass Mountains, about five thousand three hundred feet above the sea, and near the border of Sonora. A violent tremor of the earth, including two sharp shocks, and lasting over ninety seconds, was succeeded at fre

quent intervals by many lesser movements in the next three days, and less frequently at least up to May 29. In this part of Arizona solid house-walls, of adobe, or unburned brick, were cracked or overturned, while huge rocks in the steep mountain gorges rolled down, causing much damage. Fires, perhaps kindled by these in their course, appeared immediately afterwards in various wooded regions in Sonora and Arizona, giving rise to many false rumors of volcanic eruptions. The movement here seemed from south to north; the Sonora railroad track in one place near the frontier, running east and west, was displaced three inches to the north; while a chimney-shaft, without being overturned, was turned violently around upon its base. The small town of Bavispe in the Sierra Madre, in Sonora, was nearly destroyed, many people being killed and wounded. Opoto suffered in a similar way, and Fronteras to a less extent. The district chiefly affected by the earthquake is, however, for the most part a desert, with some cattle-ranches and mining stations.

Interesting studies were made by the authors in the valleys, or mesas, between the parallel mountain ridges in this region, both in the San Pedro and Sulphur Spring Valleys. The latter, lying to the east of Bisbee, and stretching north and south about one hundred miles, is often eight or ten miles wide, and has its lower portion in Sonora. Though without a visible water-course, water is there generally found at depths of from ten to forty feet in the numerous wells sunk at intervals to supply the needs of large herds of cattle. As described by many observers, the surface of this plain was visibly agitated by the first earthquake shock, so that persons were in some places thrown down by the heaving of the soil, which burst open, with discharges of water, while the wells overflowed and were partially filled with sand. In the southern part of this valley, for about seven miles south from the Mexican frontier, the authors found the results of the undulatory movement of the soil apparent in great numbers of cracks and dislocations. For distances of several hundred feet, along some lines with a generally north and south course, vertical downthrows on one side, of from one foot to two feet and more, were seen, the depressed portion rising either gradually or by a vertical step to the original level. Branching, and in some cases intersecting, cracks were observed. These depressions were evidently connected with outbursts of sand and water, which, along cracks,-marked by depressions on both sides,sometimes covered areas of many hundred square feet with layers a foot or more in depth, marked here and there by craters two feet or more in diameter, through which water had risen during the outburst of these mud volcanoes. The authors examined many of these phenomena in Northern Sonora, and took photographs, which were exhibited. They note that while the