100 ORTMANN — AFFINITIES OF CAMBARUS. [April 13, 
tively of C. gractlis and of C. advena (Hyeme vitam degit subter- 
raneam. Aestate in fossis.invenitur. Leconte). 
The large number of species known in the third section makes a 
further division desirable, which is easily made according to the 
following characters : 
1. Group: (spiculifer). 
Outer part of sexual organs with two or three recurved teeth, with- 
out prominent angle (shoulder) on anterior margin. Rostrum with 
marginal teeth, acumen rather long. Areola wide, rarely narrow, 
distinctly shorter than half of the anterior section of the carapace. 
2. Group: (blandingt). 
Outer part of sexual organs with three (rarely two) recurved 
teeth, tnner part with terminal spine directed obliquely outward. No 
shoulder on anterior margin. Rostrum with marginal teeth, acumem 
rather short. Areola narrow, generally distinctly longer than half 
of the anterior section of the carapace. 
3. Group: (clarkt). 
Outer part of sexual organs with two compressed tubercles, inner 
part straight, directed forwards. Antertor margin with a distinct 
shoulder. Rostrum with marginal teeth, acumen rather short. 
Areola very narrow, often obliterated in the middle, about half as 
long as anterior section of carapace. 
4. Group: (allen). 
Outer part of sexual organs with one or two teeth, often pecularly 
formed (compressed and plate-like), inner part straight or oblique. 
LVo shoulder on anterior margin. Rostrum without marginal teeth 
(at least tn the adult stage). Areola moderately wide, about half as 
long as anterior section of carapace. 
There is no doubt, that the sfzculifer-group is the most primitive 
of these, and that the others represent special modifications, each 
developed in a different direction. 
The following key for the identification of the species of the sub- 
genus Caméarus is submitted ; it is claimed that this key represents 
—as far as is possible ina ‘‘ key’’ —the natural affinities. If adult 
males of the first form are at hand, it should be possible, in every 
case, to correctly identify the species. 
1. Section of C. digueti (see p. 98). 
a, Sexual organs of male with only one terminal tooth on outer part, inner part 
with two tips ; anterior margin with an angular projection (shoulder) near 
the tip (diguett-group). 
