96 DIPLOPODA. 
Head and first tergal plate smooth. Inferior area of first plate abruptly incurved and marked with ridges 
defined by grooves, the superior ridge forming a cariniform crest with a somewhat tuberculiform posterior 
enlargement. The crests on the succeeding segments thick. Posterior half of segments and area 
of anterior half immediately in front of the groove very finely and closely punctured. Pores beginning 
on the fifth segment. Anal segment with tergal plate marked posteriorly with a transverse depression 
marking off a somewhat nodular caudal prominence, which scarcely covers the summit of the valves; 
the latter with strongly compressed and prominent edges; sternal plate with posterior edge almost 
straight. 
Number of segments 57-65. 
Length, according to Brélemann, up to 121 millim., with a width of 7:20. 
Hab. Mexico, Ciudad in Durango (Forrer); Costa Rica, La Palma, Surubres near 
San Mateo, Caché (Biolley !), Cariblanco (Lankester *). 
The brief diagnosis given above is taken from a single female example, collected by 
Forrer at Ciudad, which, judging from the description, is indistinguishable from the 
specimens from Costa Rica assigned by Brélemann to O. typotopyge. ‘This specimen 
has 57 segments, and about 75 mm. in length and 6°8 in width. According to 
Brélemann, the anterior lamina of the coleopod in the male is inferiorly ewarginate ; 
and the posterior lamina is distally expanded into an antero-posteriorly compressed 
plate, with strongly convex lower edge, and produced externally into a short, blunt, 
upwardly directed process. 
2. Orthoporus palmensis. 
Spirostreptus (Scaphiostreptus) typotopyge palmensis, Brolemann, Ann. Soc. Ent. France, Ixxiv. 
p. 362, t. 9. fig. 18 (1905) ?. 
Hab. Costa Rica, La Palma (Diolley '). 
Described by Brélemann as easily distinguishable from the typical form of O. typo- 
topyge, of which he considered it to be a subspecies, by having the inferior angles of 
the first tergal plate less sharply incurved and marked with shallower grooves, by 
having the sculpture of the segments coarser and more striolate, and by certain details 
in the structure of the copulatory apparatus—for example, the anterior plate of the 
coleopod is distally rounded, instead of being slightly concave, and the external process 
of the distal end of the posterior plate is slenderer and a little longer. The figures 
of this apparatus in the two forms show, however, very marked differences in the latter 
respect, for the whole distal extremity of the plate in question is shorter and much less 
expanded in O. palmensis than in O. typotopyge, and the external process in the former 
has the form of a strong, stout, upcurled hook, whereas in the latter it is merely a 
short, blunt projection. It appears also from the description that the posterior end of 
the anal tergal plate is less lobate and less sharply defined by the transverse groove, and 
that the margins of the anal valves, although compressed, are defined by a shallower 
depression in O. palmensis than is the case in O. typotopyge. ‘These facts, coupled 
with the circumstance that specimens of the two forms were taken together at 
