417 



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 Naso- 



Family Pterodesmid^e, New. 

 This family is proposed for Po(y<U',<m>i* ijnln>ni>-n.* Lucas and its 

 African relatives, by more recent writers referred to Cryptodesmus. I 

 have examined the type of Cryptodesmus olferrii in the Berlin Museum. 

 The diversities seem to be of family importance. The African forms 

 are very curious, the development of the lateral carina 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 have 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 mar- 

 gin, in the anterior part of the carinse, 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 browneltii, t he- 

 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. Compso- 

 desmus 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 be- 

 tween it and the posterior margin on each side is nearly white or bright 

 yellow. Carina? tinted with bright orange or pink, or both. Below, 

 except near the edges of the carina?, the body is covered with a pure 

 white bloom or chalky powder. Last segment nearly white. Motions 

 very sluggish. 



