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has proved necessary to establish genera and families in attempting to properly recognize their structural novelty and diversity. Some of these new groups have already received names, but their characters have been only formally indicated.
Family AMMODESMIDE. Two minute Glomeroid genera were discovered, one of which, Ammodesmus, is the smallest member of the suberder, if not of the entire class. The only species, Ammodesmus granum, is less than two millimetres long, and about half a millimetre broad. A single specimen was secured while collecting minute Oniscidæ, but diligent and repeated search failed to find another. It did result, however, in three specimens of a very distinct, though evidently allied, genus which it is proposed to name Cenchrodesmus. Both genera have the habit of coiling into a sphere. The second segment is enormously enlarged so as to completely conceal the head and first segment when viewed from the side, as well as to cover the space left between the decurved carinæ of the other segments when the creatures are coiled. Ammodesmus has the dorsum roughened by a transverse row of large papilliform tubercles rising from the posterior part of each segment, while Cenchrodesmus volutus has the segments nearly smooth. The surface of Ammodesmus is rough and dusted with earth. When disturbed it coils up and lies motionless, and is then perfectly concealed, having exactly the appearance of a grain of sand. My specimen would certainly not have been seen had it not been crawling. Cenchrodesmus is pinkish in life and mottled with pale horn-color in alcohol. Both genera live on the ground under decaying wood or leaves.
Family CAMPODESMIDÆ. This also contains two genera similar in size and general shape, yet evidently distinct, in that Campodesmus has the segments ornamented with two conspicuous clusters of coarse tubercles, while Tropidesmus jugosus has two transverse rows of short longitudinal carinæ, a form of sculpture previously quite unknown in Polydesmoidea. The carinæ are depressed in both genera, and the dorsal surface is very rough with fine granules and tubercles. Pores are visible on the fifth and seventh segments, but I have been unable to find them on the others. Both forms are denizens of the deepest forests, where the light is so deficient that they are sure to be overlooked unless specially sought for. They are very sluggish in their movements, and are seldom found crawling. When disturbed they coil up into a spiral, and also assume that posi
? Proc. U. S. Nat. Museum and Annals N. Y. Acad. Science, 1895.
tion in alcohol. The first segment is not enlarged to conceal the head, nor are the anterior segments larger than the others. The general appearance is strikingly different from that of other Diplopoda, the resemblance being rather to certain lepidopterous larve.
Familly COMODESMIDÆ, new. The type of this family is a small, reddish-brown, subcylindrical form, very rare, and also inhabiting the denser parts of the forest. The pore-formula is unique : 5, 7, 9, 12, 15, 17, 18. The pores are located in the front part of the posterior subsegments. The dorsal surface is beset with conic piliferous granules, giving a wooly appearance. The last segment is scarcely produced beyond the anal valves, but is rounded off at apex as in many Iulidæ. The head is not concealed by the first segment, which is narrower than the second and somewhat included between the carinæ of the latter, much as in Scytonotus granulatus (Say). Two other allied genera, also granular and hairy, are found in similar situations in Liberia, but both have the normal poreformula as in Polydesmus. Thelydesmus is nearly black, larger and much more abundant than Comodesmus. The generic name alludes to the fact that the females are in a large preponderance. Although about a hundred females were taken, careful and extended collecting resulted in only four males. The remaining genus is minute and very rare, cylindrical, and without carinæ. The posterior subsegments are abruptly thicker than the anterior, giving the appearance of a series of of discs laid together, whence the generic name, Discodesmus. In the Berlin Museum is another form evidently allied to Thelydesmus, but with broader carinæ and more resemblance to the Pterodesmida, to be Doted later on. It was collected in the German Colony of Togo by Dr. K. Büttner, and may be known as Xyodesmus planus.
In addition to the above genera there may be referred to this family Cylindrodesmus Pocock, from Christmas Island. It is even more evidently allied to Comodesmus than the other genera mentioned. There is also in my collection a new generic type from the mountains of Java, not closely related to the other genera, but evidently belonging to the same family group.
Family PREPODESMIDÆ, new. Under this name it is proposed to arrange West African forms hitherto referred either to Paradesius or to Oxydesmus, from the latter of which they differ in having the apex of the last segment narrow and bituberculate. The affinities of the group seem to be with the Oxydesmidæ, although no connecting links have yet turned up. In a
large number of forms the poriferous segments are wholly or partly red or yellow, while the remainder of the body is nearly black, giving a most striking appearance. Prepodesmus includes several such forms, all with the anterior corner of the second segment greatly produced and embracing the first segment. Tylodesmus has the corner rounded and not produced. Cheirodesmus is similar to the last in general shape, but is more slender and with the male genitalia resembling in shape a gloved hand. Anisodesmus is peculiar in that the fourth segment is distinctly, though slightly, narrower than the third or fifth. The species are uniform dark red in color and the type is closely allied to Polydesmus erythropus Lucas. Isodesmus is evidently related, but with the fourth segment not narrowed, and remarkable in that the pores are not borne on a distinct callus as in the other genera of the group. The copulatory legs are also very peculiar being deeply divided into several lacinia. In all these genera the dorsal surface is finely and evenly granular, though differing somewhat in other respects. The family is probably distributed along the entire West Coast, and I have seen two forms from South Africa, one of which, Lipodesmus, is in the Berlin Museum.
Family OXYDESMIDÆ. The Liberian forms which belong to this family in the more limited sense are all referable to the genus Oxydesmus, and belong to three species, 0. grayii Newport, 0. medius and O. liber, both new. The first is a very striking form, black in color with a narrow median stripe of bright vermillion. The other species are also black, 0. liber with bright yellow submarginal ridges.
Family POLYDESMIDA. Of Liberian species referable to this family in its stricter sense there seem to be but two; small pinkish-red forms, similar in general appearance to some species of Brachy desmus. The dorsal elevated areas are each supplied with a clavate hair. The antenna are strongly clavate, though rather slender, and the second pair of legs is crassate in the male. For this genus the name Bactrodesmus is proposed; it will probably be found to be next related to the form described from Ceylon by Humbert as Polydesmus cognatus, but which is generically different from the European P. complanatus, and may be denominated Nasodesmus.
3 The African forms having the apex of the last segment broad, the femora spined, and the carinæ with a submarginal ridge, constitute the family Oxydesm. idæ. There are five genera now known, two confined to the east side of the continent, three to the west. Of the east coast forms, Orodesmus includes those with strongly tuberculate segments, Mimodesmus those with the body slender and the dorsum nearly smooth. Of the west coast genera Oxydesmus has three rows of dorsal tubercles and surrounding areas; Scytodesmus has five or six rows, while Plagiodesmus resembles Oxydesmus, but has the submarginal ridges very broad and oblique, and the copulatory legs large and exposed.
Family PTERODESMIDÆ, New. This family is proposed for Polydesmus gabonicus Lucas and its African relatives, by more recent writers referred to Cryptodesmus. I have examined the type of Cryptodesmus olfersii in the Berlin Museum. The diversities seem to be of family importance. The African forms are very curious, the development of the lateral carinæ being carried to its greatest extent. They are very much flattened, elliptical in out. line, and only four or five times as long as broad. They never coil into a spiral, even when placed in alcohol. At least five genera are found in Liberia.
All the African forms yet known to me bave repugnatorial pores, and we may expect to find these in the others, notwithstanding the statements of several writers to the contrary. The location of the pores is, however, very unusual. They are far remote from the lateral margin, in the anterior part of the carinæ, in some cases so far ahead as to be concealed by the posterior margin of the preceeding segment. An even more remarkable condition obtains in Pterodesmus brownellii, the type of the genus and family. The fifth segment has no pore ! The Liberian forms are further peculiar in that all are more or less pruinose. Pterodesmus is the largest of the Liberian genera. It is pure white when young, but mature individuals are usually dusted with earth which adheres to the pruinosity and gives them the advantage of protective coloration. Gypsodesmus, on the other hand, is pure white, even when mature. Lampodesmus is partly pruinose and appears to be black and white when alive, though it is brown in alcohol. It is structurally peculiar in that the sternum of the sixth segment bears two hollow processes fringed along their apical edges with long hairs. These may be of use as a protection to the copulatory legs. Compsodesmus is the broadest of the Liberian forms. When alive it is one of the most varied and brilliant of Diplopoda. A large median area of the dorsal surface of each segment is dark brown, while the space between it and the posterior margin on each side is nearly white or bright yellow. Carinæ tinted with bright orange or pink, or both. Below, except near the edges of the carinæ, the body is covered with a pure white bloom or chalky powder. Last segment nearly white. Motions very sluggish.
From the German colony of Togo comes a genus evidently allied to the last, but distinct by reason of the more slender body and narrower carinæ, which are also scarcely produced at the posterior corners. From Lampodesmus it is distinct in the absence of the process from the sternum of the sixth segment, and in the form of the copulatory legs.
A small horn-brown or yellowish creature with remarkably agile movements it is proposed to name Choridesmus citus. The first segment is pure white, pruinose, and abruptly different in color from the remainder of the body. The pores are large, and are located in the middle of the carinæ, remote from the margins. The quick, jerky movements remind one strongly of Polyxenus.
Family STRONGYLOSOMATIDÆ. Of this group there are two genera in Liberia, both new, though probably not confined to the West Coast. Scolodesmus grallator represents the usual Strongylosoma type, with long legs and antennæ. It is dark wine-color, nearly black. Habrodesmus lætus is a rare species apparently confined to the darkest forests. It is exceedingly quick and agile, very graceful in form and brilliantly colored. The legs are orange and pink, and the segments have the posterior margin yellow, shading through orange and brown to black on the remainder of the segment.
In gardens at Monrovia Orthomorpha vicaria (Karsch) is not uncommon; it is probably not indigenous.
Family STYLODESMIDÆ, The type of this family is a bizzare creature named Stylodesmus horridus. The generic name alludes to the fact that the pores are borne on long stalks placed near the lateral margins of the broad, decurved carinæ. The pore-formula is the usual one, 5, 7, 9, 10, 12, 13, 15-19. The whole dorsal surface of the animal is setose and coal-black. There is almost always an incrustation of dirt which furnishes a completely protective coloration. The head is completely concealed under the flabelliform, anteriorly lobed, first segment, and the last segment is reduced, included in, and concealed by the penultimate. The most striking feature is that each of the segments except the last bears dorsally a pair of long slender processes.
Those of the anterior and posterior segments are close together and show a tendency to unite at the base. These processes are also rough and setose, and almost always so incrusted with dirt as to appear several times their actual size. If segments of Stylodesmus had been found in fossil condition they would probably have been looked upon as allied to some of the