108 ORTMANN — AFFINITIES OF CAMBARUS. [April 13, 
(digueti-group), and that the development of an additional pair of 
hooks on the fourth pereiopods is a parallelism to the similar ten- 
dency in the more highly advanced forms of the subgenus Camdbarus 
(dlandingi group) : to the latter, C. pe//ucidus has no direct relation 
at all. 
With regard to all the rest of the species of this subgenus, I 
agree with Faxon in thinking them to form a natural, genetically 
connected group. Nevertheless there is much diversity within 
this subgenus, and is chiefly indicated by the shape of. the male 
sexual organs. Faxon did not use the latter in arranging the 
species of his fourth group, and thus his key (1885, p. 86) is, as 
he admits himself, artificial to a degree. But I shall show here, 
that according to the sexual organs we can divide the subgenus in 
groups, which seem to be quite natural. 
1. Section: C. limosus. 
Sexual organs short, rather thick up to near the tips, reaching to 
the base of the third pair of pereiopods. Tips split for a short 
distance, each tapering to a point. Hooks on third, or on third and 
fourth peretopods. 
This is the most primitive section of the subgenus, and it is also 
in other characters quite indifferent, and not highly specialized ; 
and further, it appears a little heterogeneous. ‘The rostrum is 
quite uniform in shape, generally with marginal spines (except in 
certain varieties of C. ped/ucidus), with a rather long or a moderate 
acumen. ‘The areola is wide and of medium length (except C. 
pellucidus); the chelze are comparatively narrow and without 
remarkable features (except in C. harrison). 
The annulus of the female shows the tendency to develop tuber- 
cles upon its face; these tubercles have a more or less central 
position (“mosus, indianensis), or a posterior (sloanez), or have 
the shape of a transverse ridge (harrison’), or form a ‘‘ median 
keel’? (fellucidus). 
2. Section: C. propinquus. 
Sexual organs shorter or longer, not thick, deeply split at the tips, 
tips slender, more or less straight, sometimes the outer one slightly 
curved, but never both tips curved in the same direction. Always 
only third peretopods with hooks (barring freaks). 
The other characters are very uniform in this section. The 
rostrum possesses with one exception (C. medius), marginal spines, 
