470 MEMOIRS OF THE CARNEGIE MUSEUM 



1 . Camharus obscurus. 



Nothing whatever was previously known in regard to tlie Hfe-hist(jry 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 ( Marcli) 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, !)ut all agree in having a rather 

 dirty (mud-incrusted) shell, a sure sign that tlie shell is old and that no recent 

 moulting has taken place. Tliere 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 newlv moulted males which are of the second foi-m. It seems, however, that 

 in exceptional cases rather young males (30 to 40 \nm. long) may have gone through 

 the winter in the second form. The size of tlie males of the first form varies greatly; 

 tlie 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 impoi'tant 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 tliese dates. But on April 6, 1905, 

 (in Thorn's Ci'eek, Renfrew, Butler ( 'uunty), 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 : A}>ril 0, 1905 ; April 10, 1905 ; 

 April 1<), 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 



