se) ORTMANN 
form), in which they have disappeared, is 58 mm. long, but in 
another, 62 mm. long, they are still recognizable. Three other 
males of the first form, 69, 71, 72 mm., have no spines. In 
the females, the spines generally persist up to a size of 60 and 
62 mm., but they are missing in two females of 62 and 68 mm. 
length. 
Cambarus pilosimanus is Closely allied to C. wellzamsont Ort- 
mann! from Los Amates, near Izabal, Guatemala. Indeed, it 
may be identical with it. The difference of the pilosity of the 
chele in old individuals of C. prlosemanus is very marked how- 
ever, but we are to bear in mind that the largest individual of C. 
williamsoni was rather small(51.5 mm.). Aside from the pilos- 
ity of the chele, the only important difference noted is in the 
male copulatory organs, C. pzlost¢manus having the shoulder 
less developed, and the tips of the inner and outer part more 
strongly contrasted. But this difference is not necessarily spe- 
cific, since for the rest the copulatory organs of both species are 
built according to the same plan. Other differences are only 
slight and apparently unimportant. In the young of C. fzlosz- 
manus, where the pilosity of the chelz is not developed, the car- 
popodite and meropodite always possess a number of sharp 
spines, while in C. wzllzamsonz only in the very young are 
traces of such spines visible on the meropodite. In specimens 
of about the same size, the granulations of the hand are more 
distinct in C. wz7lliamsonz, although in old individuals of C. 
pilosimanus the granules are much stronger than in any speci- 
mens of C. wzlliamsoné that are known. Further, the hand of 
C. pilosimanus is comparatively less slender, and is broader 
than in C. wlhamsonz. . 
The close affinity, if not identity, of these two species is also 
borne out by the geographical distribution, but the two known 
localities of C. pzlostmanus are farther north than that of C. 
williamsont. It is quite possible that additional material will 
demonstrate their identity, but for the present I separate them, 
since there is no individual among the material from the prov- 
ince of Izabal that shows any trace of the pilosity of the chele. 
1 Ann. Carnegie Mus., III, 1905, 439. 
