i6 
XYODESMIDAl. 
this series Peridontodesmus Silv., founded on Scytonotus woodianus 
(H. & S.) may probably be added. It will be distinguished from the 
American, and indeed from all the forms mentioned above, by the 
coarsely dentate segments ; but as nothing is known with regard 
to the location of the pores, it could not well be included in the 
synopsis. Neither this genus nor Trachelodesmus has any appa- 
rent relationship with Scytonotus C. L. Koch, such affinity having 
apparently been inferred without an examination of the types. 
KEY TO THE GENERA OF XYODESMIDvE. 
Segments 2-3 or 2-4 each with a pair of tubercles hypertrophied into long 
horn-like processes: Genus Diaphorodesmus (Silv.), type D. dorsicorms 
(Prt.), Kamerun. 
Segments with tubercles subequal. ........ 
Last segment broad and lamellar, basally emarginate on the sides so as to ap- 
pear constricted ; no distinct tubercle or conic process on the sides of the 
apical portion of the segment: Genus Cryptoporus (Prt.), type CV. verrucosus 
(Prt.), Kamerun. 
Last segment with a more or less narrowed truncate apex, and with a more 
or less distinct marginal tooth or process on each side of the apex proper ; in 
cases where this tooth is small the sides of the apical portion distinctly con- 
verge. .............. 
Pores located under the apices of the small carinae of segments 5, 9, ii, 14, 
16, facing laterad; sternum of last pair of legs with two long spines ; segments 
19: Genus Batodesmus, nov., type B. alutaceus (Ptrs.) ; Bogota. 
Pores, if present, with the usual formula, 5, 7, 9, 10, 12, 13, 15-19; carime 
either not narrowed or only the first three or four ; sterna either without 
spines or those at the base of the la.st legs are not larger than those on 
the middle segments. ........... 
Repugnational pores located in distinct excavations in the lateral margins of 
the carinae ; dorsum very slightly convex ; last segment with the marginal 
processes very strongly developed : Genus Scaptodesmus type Sc apt 0- 
desmus porati, sp. n. {Parades 77 ius erythropus Prt., non Lucas), Kamerun. 
Repugn atorial pores, if evident, located in a distinct marginal tubercle or 
callus, or the dorsum is strongly convex and the last segment has the marginal 
tubercles slightly developed. 
All the carinae broad and moderately long ; pores evident, located in a dis- 
tinct, marginal, bead-like callus: Genus Thymodesmus, 7 iov., type Th. pulvi- 
7 iar, sp. n., Kamerun. 
Either the anterior carinae are evidently shortened, sometimes into spine-like 
processes, or the pores are not located in a marginal callus. 
Segments densely beset with sharply conic granules ; the edges of the rather 
broad horizontal carinae sharply dentate with somewhat larger cones ; anterior 
segments without enlarged tubercles; last segment with marginal processes 
well developed; pores obscure; sterna not spined : Genus Xyodesmus Ck., 
type X. pla 7 ius Ck., Togo. 
Segments above beset with rounded granules or tubercles ; carinae very 
narrow ; anterior segments shortened, with a transverse row of large tuber- 
