402 MEMOIRS OF THE CARNEGIE MUSEUM 
Other freaks are occasionally found, as for instance a specimen without an acumen 
on the rostrum, the latter being evenly rounded off; a specimen with the immov- 
able finger of the left hand with a double tip, the outer one the larger, and a spec- 
imen with the movabie fingers of both hands only half as long as usual, thick, short, 
and conical. Such cases apparently are due to some previous injury, and suggest 
nothing of special interest. 
All the variations mentioned above are rare and are not restricted to certain 
parts of the range of the species, so that we do not distinguish any regional varieties. 
ls 
7. CAMBARUS (BARTONIUS) DIOGENES Girard. 
(Plate A, Fig. 3; Plate XX XIX, Fig. 11; Plate XL, Figs. 6 and 7.) 
Cambarus diogencs Girard, 1852, p. 88; Faxon, 18846, p. 144; Abbott, 1884, p. 1157; Faxon, 1885a, p. 71; Faxon, 
1885b, p. 359 ; Faxon, 1885c, p. 140; Underwood, 1886, p. 368; Faxon, 1890, p. 624; Ortmann, 1891, p. 12; 
Hay, 1896, p. 489, Fig. 7; Faxon, 1898, p. 650; Osburn & Williamson, 1898, p. 21; Williamson, 1899, p. 20, 48; 
Hay, 1899, p. 959, 961 ; Harris, 1900, p. 267 ; Williamson, 1901, p. 11; Hay, 1902a, p. 235 ; Ortmann, 1905a, p. 398. 
Cambarus obcsus Hagen, 1870, p. 81, pl. 1, £. 39-42, pl. 3, f. 163, pl. 9; Smith, 1874, p. 639; Forbes, 1876, p. 5, 19; 
Bundy, 1877, p. 171; Bundy, 1882, p. 183; Bundy, 1883, p. 403. 
Cambarus diogenes ludovicianus Faxon, 1884b, p. 144; Hay, 1€99, p. 959, 962. 
Cambarus dubius Osburn and Williamson, 1898, p. 21, (non dubius Faxon). 
Cambarus ( Bartonius) diogenes Ortmann, 1905b, p. 120, 135. 
Body robust, smooth, except for short hairs, chiefly on the chelee in fresh shells; 
the hairs also to a certain degree persist upon the hand and fingers in older indi- 
viduals. 
Carapace subovate, not depressed, but rather compressed. G:H:B=1:0.88 to 
1.0:1.06 to 1.2; that is to say, the transverse diameter of the carapace is very 
slightly greater than the vertical, at the hepatic region sometimes even less. Great- 
est width of branchial regions well forward, not far from the cervical groove. 
Cervical groove deep, not interrupted on the sides. 
Areola distinctly longer than half of the anterior section of the carapace (a: p = 
1:0.61 to 0.75), very narrow, and generally obliterated in the middle; that is to 
say, the two lines bordering the branchial regions are in contact in the middle of 
the carapace. In rare instances a small space is left between them, upon which 
there is no room for punctures. 
Rostrum more or less lanceolate, rather narrow, but not very long, reaching 
hardly beyond the distal end of the second joint of the peduncle of the antennula, 
being often shorter. Upper surface slightly concave, with elevated margins. Mar- 
gins not much swollen, the swelling gradually disappearing toward the tip, con- 
verging, straight, or slightly convex, contracted to form a short triangular acumen. 
Basal angles of acumen indistinct, rounded, without any trace of marginal spines. 
