388 MEMOIRS OF THE CARNEGIE MUSEUM 
ten young ones, ready to leave the mother, (very likely a number had left already 
when the mother was captured). It has on the ischiopodite of the left third perei- 
opod the copulatory hook of the male; this hook is not small or rudimentary, but 
strong, and similar to the hook as found in the male of the first form. The ischi- 
opodite of the corresponding right pereiopod has no trace of this hook. 
2. A specimen, 48 mm. long, was found in Fern Hollow, Pittsburgh, November, 
22, 1905, (Cat. No. 74. 681), which externally (in the shape of the claws) looks like 
a female, but shows very indistinctly the sexual openings of the male, and no traces 
of those of the female. It also has the first pleopods of the male of the second form, 
but the second pleopods are built according to the female type. Further, it lacks 
entirely the hooks of the third pereiopods, and has a distinct female annulus, of 
juvenile type. 
This case does not correspond exactly to any of those described previously. It 
resembles to a certain degree one of the cases in C. obscurus described above (No. 3), 
with the exception that here the first pleopods are of the type of the male of the 
second form, and that the second pleopods are not of the male, but of the female type. 
4a. CAMBARUS (BARTONIUS) BARTONI ROBUSTUS (Girard). 
(Plate B, Fig. 2. Plate XX XIX, Fig. 2a.and 26. Plate XL, Fig. 3.) 
Cambarus robustus Girard, 1852, p. 90; Hagen, 1870, p. £0, Pl. 3, f. 167; Smith 1874, p. 639; Faxon, 18846, p. 143. 
Cambarus bartoni robustus Faxon 1885a, p. (1; Faxon, 1885), p. 358; Underwood, 1886, p. 367; Faxon, 1890, p. 622; 
Faxon, 1898, p. 649 ; Osburn & Williamson, 1898, p. 21; Williamson, 1899, p. 20, 47; Hay, 1899, p. 959, 966 ; 
Williamson, 1901, p.11; Ortmann, 1905a, p. 391; Ortmann, 19050, p. 135. 
Cambarus bartoni Williamson, 1905, p. 310. 
The differential characters of this form are the following : 
Body robust, attaining decidedly a more considerable size than the typical bar- 
tom. The largest individuals at hand are a male, first form, from Spartansburg, 
Crawford County, measuring about 98 mm. (estimated, since rostrum is damaged) ; 
a female from Squaw Run, Allegheny County, measuring 94 mm. and a male, 
second form, from Puketta Creek, Allegheny County (A. Keenig coll.), measuring 
101mm. I have quite a number of males (of the, first and second form) and of 
females over 90 mm. long. It is also remarkable that specimens of this variety, of 
a considerable size (6V to 70 mm.) display characters which are distinctly juvenile, 
showing no tendency on the part of the chelee to attain a large size. This tendency 
is also evidenced by the fact that the smallest males of the first form at hand are two 
individuals measuring 72 mm. (Union City and Hulton). From Oberlin, Ohio, I 
have seen a male of the first form, 71 mm. long, while the minimum size of sexually 
ripe males of the typical form is 50 mm. for western, and 4) mm. for eastern 
Pennsylvania. 
