470 MEMOIRS OF THE CARNEGIE MUSEUM 
1. Cambarus obscurus. 
Nothing whatever was previously known in regard to the life-history of this 
species, I have observed it during the larger part of two seasons, the dates of actual 
observation covering the time from March 28 to November 19 (in 1904 and 1905). 
Beginning in spring (March) it is ascertained that the species is at this time quite 
active, being found in the usual localities (under stones in rivers and streams), and 
the specimens are of various sizes and conditions, but all agree in having a rather 
dirty (mud-incrusted) shell, a sure sign that the shell is old and that no recent 
moulting has taken place. ‘There are occasional specimens with a very clean shell, 
in which moulting has occurred quite recently. This teaches us that during the 
winter months as a rule moulting does not take place, but that it begins quite early 
in spring, although only in the case of a few individuals. Males of the first form 
are abundant at this time, while males of the second form are scarce, and it is chiefly 
these newly moulted males which are of the second form. It seems, however, that 
in exceptional cases rather young males (30 to 40 mm. long) may have gone through 
the winter in the second form. ‘The size of the males of the first form varies greatly ; 
the smallest found by the writer in spring (May 2, 1905) measure 40 mm. in length, 
but specimens between 40 and 50 mm. long are very abundant. All the males 
between 30 and 40 mm. long are of the second form, but they are not abundant, as 
has been stated. ‘The smallest male found in spring was 31 mm. long. The condi- 
tion of the females in early spring corresponds to that of the males, and in this sex 
the minimum size is 27 mm. in length. 
Very soon an important event takes place in the life of the females. Eggs are 
laid. No signs of this were seen on March 28, 1905, and March 31, 1905, although 
a large number of individuals were collected at these dates. But on April 6, 1905, 
(in Thorn’s Creek, Renfrew, Butler County), numerous specimens with eggs were 
taken, some in the very act of spawning. I was able to observe in this species the 
peculiar attitude assumed by the female, and the ‘‘apron,” described by Andrews 
for C. limosus (1904, p. 180, fig. 5; p. 182, fig. 6). The same was seen repeatedly on 
subsequent dates in April, so that April is to be considered as the spawning season. 
The number of eggs is rather large, one hundred to two hundred and even more, 
but young specimens sometimes have considerably less. 
From the beginning of April onward females with eggs are found very regularly 
until the end of May. My dates are the following: April 6, 1905; April 10, 1905; 
April 19, 1905; April 24, 1905 and 1906; May 1, 1905; May 2, 1905; May 3 
1899 (Williamson and Shafer); May 4, 1905; May 8, 1905; May 17, 1906; May 
22,1905; May 25, 1905. With one exception (April 15, 1905) I found females with 
