64 A KEVISION OF THE ASTACID^. 



more gradually to form the longer acumen. The areola is wider and more 

 punctated, the antennal scale broader at the tip. This is the form described 

 by Girard under the name of C. montaims. From tliis form we easily pass 

 to one with a still more elongated rostrum, hand and fingers scarcely tuber- 

 culated, external finger bearded within at the base, antennal scale truncate 

 at the end, with the inner margin straight and parallel to the outer one. 

 The epistoma is short and transverse. This form I have called C. Bartonii, 

 var. lonffirosfm. It is perhaps the same as Girard's Camhanis longithts (see 

 p. 66). My specimens come from Eastern Tennessee and West Virginia. 

 Three from Cumberland Gap have a well-marked lateral spine on the cara- 

 pace. There are so many varieties connecting this one with the more typical 

 forms with a short I'ostrum, that I cannot i^egard it as a distinct species. 



Even among those with the short quadrangidar rostrum there is consider- 

 able variation, the upper surface of the rostrum being more or less hollowed 

 out and the margins thickened, and the areola of variable width. From one 

 locality, Cincinnati, Ohio, come three forms which are readily distinguishable 

 from each other. In one of these (M. C. Z., No. 267) the rostrum is sub- 

 quadrangular, the antennal scale narrow, and the areola narrow (2 mm. in 

 a specimen 75 mm. long) with two longitiulinal lines of dots. This comes 

 very near the common Eastern form, but the rostrum is more excavated 

 above. In another form (M. C. Z., No. 288) the rostrum is also quadrangu- 

 lar, l^ut the areola is broad (4 mm. in a specimen 91 ram. long) and thickly 

 sown with dots. The cervical groove is more sinuate, the post-orbital ridge 

 shorter. The third form (M. C. Z., No. 243) has a somewhat longer and 

 more tapering rostrum, an almost linear areola, antennal scale broad near 

 the tip, and a shorter and more conical hand. This form approaches (J. laii- 

 maniis, and may be a distinct species from C. Bartonii. 



In specimens from the Mammoth Cave, the antennoa are extremely long 

 (1| times as long as the body), the antennal scale bi'oad and sub-truncate 

 at the end ; the metacarapace is very long, and a lateral spine is evident. 

 The mar<i;ins of the rostrum are anjj-ulated at the base of the acumen, in 

 young specimens even toothed. The terminal segment of the telson is oval. 

 The largest specimen from the cave, a male of the first form, measures 

 108 mm. from tip of rostrum to posterior border of telson. 



Fabricius's description of Astacus Bartonii is as follows : — 



" A. thorace Itevi, rostro brevi, acuminato, carpis dentatis. 



" Habitat in America boreali. Prof Smith Barton. 



