476 MEMOIRS OF THE CARNEGIE MUSEUM 
is also rarely observed. The old skin splits on the back, between the carapace and 
the abdomen, and the crawfish pulls itself out gradually, leaving the empty shell 
intact. I have not made any observations on the increase of size at the moulting 
time, in the case of this species. (But see below under C. diogenes, monongalensis, 
and C. bartoni.) None of my specimens kept in captivity went through this process, 
and those found in the field immediately after or during the act were too flabby to 
be measured. Empty shells have been found now and then, but the individuals 
belonging to these had then lost their identity. Possibly, as has been observed in 
C. monongalensis, the old shells are eaten up. 
The copulation resembles throughout that of C. limosus, as described by Andrews 
(1845, p. 867, and 1904, p. 166, Fig. 1, p. 168), and only a few remarks seem neces- 
sary. ‘The male with its claws takes hold of the claws of the female at the base of 
the hand or the base of the fingers, and in shifting its position it often seizes several 
of the other pereiopods of the female. The other legs of the male are lying on the 
sides of the carapace of the female. All the legs of the female are lying close 
together on each side, directed forward. The male uses one of the fifth pereiopods, 
sometimes the right, sometimes the left, to elevate the copulating organs, and this 
leg is laid across the sternum, sticking out on the other side behind the fourth perei- 
opod. ‘The use of the hooks is the same as in ©. limosus. 
After copulation the annulus of the female contains a ‘“spermal plug,” as 
described in C. limosus. Copulation takes place repeatedly between the same 
couple, and one male may copulate in succession with several females, and one 
female with several males. This has also been observed by Andrews (1895, p. 867) 
in C. limosus, who says copulation “may be repeated by either animal with some 
other.” 
2. Cambarus propinquus and Cambarus propinquus sanbornt. 
My observations on these two forms are fragmentary, but the dates at hand make 
it certain that the seasonal history is identical with that of C. obscurus. 
For C. propinquus I have only three observations dated in the summer ; the most 
important being June 7, 1904 (Conneautville Station), when I collected a consider- 
able number of this species. As in the case of C. obscwrus no males of the first form 
were found, and all males of the second form as well as females were of medium size, 
between 47 and 60 mm. long. Specimens collected at the end of August, 1900, by 
Dr. D. A. Atkinson at Presque Isle were in the same condition (no males of first 
form), but there was with them a young female 27 mm. long, belonging apparently 
to the generation born in June. 
The rest of my material was collected on October 4 and 5, 1904, in Erie County. 
