OBSERVATIONS ON THE A ST AC ID ^E— FAXON. 659 



male, Form II, with uncommonly long rostral acumen and long-spined 

 antennal scale. The epistoma is not emarginate in front in these four 

 specimens. 



CAMBARUS ERICHSONIANUS, new species. 

 (Plate LXIV, figs. 7-12.) 



Male, Form I, — Rostrum of moderate width, sides parallel, not thick- 

 ened, lateral spines minute, acumen reaching to the distal end of 

 the antennular peduncle. Carapace cylindrical, heavily punctated, 

 lightly granulate and ciliate on the sides; lateral spines well devel- 

 oped; postorbital ridges armed with a small anterior spine; antero- 

 lateral border scarcely angulated below the eye; areola of moderate 

 width, but little longer than the distance from the cervical groove to 

 the lateral spines of the rostrum. Abdomen as long as the cephalo- 

 thorax. Epistome triangular, often truncate or notched in front. Car- 

 pus of chelipeds with an internal median and inferior median spine. 

 Chela broad, inflated, setiferous, fingers somewhat longer than the palm; 

 internal margin of palm with a double row of depressed tubercles. 

 First pair of abdominal appendages straight, without any prominent 

 angle or shoulder on the anterior border, bifid, the two branches slender 

 and acute, reaching forward to the base of the second pair of legs. 



In the second form of the male the first pair of abdominal appendages 

 are thicker, blunter at the tips, and not horny, as in the first form. 



In the female the anuulus ventralis is depressed, only very imper- 

 fectly bituberculate in front, the hind border more prominent than the 

 front border, the central fossa obsolescent. 



Dimensions of a male, Form I: Length 70 mm.; cephalo-thorax35mm.; 

 areola 11 mm.; rostrum 5 mm.; chela 25 mm.; dactylus 15.5 mm.; 

 breadth of chela 6 mm. 



Rip Roariug Fork, five miles northwest of Greeneville, Tennessee; 

 Eastanaula Creek, Athens, Tennessee; Matlock Spring Creek, near 

 Athens, Tennessee; Big Cahawba Eiver, Alabama. (Colls. U.S.N. M. 

 and Mus. Comp. Zool.) 



In large males, Form I, the inner branch of the first abdominal 

 appendages is somewhat enlarged and spoon-shaped at the tip. 



This species has the facies of C. spinosus, but the male appendages 

 are nearly like those of C. propinquus, although the rami are a little 

 longer. Comx>ared with C. spinosus, the rami of the sexual appendages 

 in the male, Form I, are much shorter, and there is no angle or shoulder 

 on the anterior margin of these appendages; in the second form of the 

 male of C. erichsonianus the sexual appendages are much shorter and 

 blunter than in C. spinosus, and the two rami are of equal length. 

 The female of C. spinosus, may be distinguished from the present species 

 by the prominent anuulus ventralis with bituberculate anterior border 

 and deep transverse central fossa. G. propinquus, compared with 

 C. erichsonianus, is distinguished by its more ovoid cephalo-thorax, 



