490, MEMOIRS OF THE CARNEGIE MUSEUM 
In this species the young of one litter seem likewise to grow at a different rate. 
Thirteen young found with the mother in the same hole on May 2, 1905, were 
between 16 and 21 mm. long. ‘Ten young found on June 16, 1904, were from 20.5 
to 32.5 mm. long. Twenty-two young, found on July 20, were from 22 to 27 mm. 
long. Twenty-four specimens dug out with the mother by Rhoads and William- 
son *t on September 24, 1898, are from 19 to 29.5 mm. long. 
Thus it seems that C. monongalensis agrees well with C. barton. No well-marked 
spawning-season is present. At any rate the spawning-season extends over a very 
large part of the year, and, correspondingly, no well-marked mating-season can be 
distinguished. Males of the first form may be found at any time, and also males of 
the second form. Sexual maturity is delayed, males turning into the first form 
comparatively late, and the females also are not mature before they have reached a 
larger size than the river species. In all these respects, except sexual maturity, C. 
monongalensis differs from C. diogenes. 
There are further differences from C. diogenes in the development of the young. 
We have seen that young C. diogenes remain in the hole of the mother for some time 
after they have left the abdomen of the latter. When hatched they are about 9 or 
10 mm. long, and leave the mother very soon, since free individuals have been found 
only 10 mm. long. When they have grown to about 20 mm. in length, they leave 
the hole of the mother. 
In C. monongalensis, however, they stay considerably longer in the hole of the 
mother. The exact time cannot be ascertained, but we can draw conclusions from 
their size. Free young specimens from 13 to 25 mm. in length are always found 
with the mother. The smallest specimen which had begun to make a hole of its 
own was 26 mm. long (August 7, 1905, Fern Hollow). Another was 29 mm. long 
(October 28, 1905, Edgewood Park). Specimens over 80 mm. long generally have 
built their own burrows. But there are exceptions. As we have seen, young up to 
32.5 mm. long have been found with the mother; and further, on July 24, 1905 
(Deer Lick), I took out of one hole fifteen young, measuring from 27 to 33 mm. in 
length, and out of another hole three young measuring 37, 39.5, and 40 mm. in 
length. In these cases the mother was also in the hole. Although in the last two 
cases conditions seem rather abnormal, it is certain that the young of C. mononga- 
lensis remain longer in the hole of the mother than those of C. diogenes. While the 
latter begin to shift for themselves when about 20 mm. long, young specimens of 
C. monongalensis do not do so before they reach 25 or 80 mm. in length, and may 
even postpone this step till they have attained a larger size (maximum 40 mm.). 
1 Williamson (1901, p. 12) says that there were forty-seven young ones: only twenty-four are now in the collec- 
tion of the Carnegie Museum (Cat. No. 74. 25). Possibly this discrepancy is due to a misprint. 
