N0.1J36. OBSERVATIONS ON TEE AST ACID.B— FAXON. 689 



tubercles, liands swollen, rounded above and below, slijjhtly tubercu- 

 late on their upper margin, and scarcely punctate. The anterior proc- 

 ess of the epistorae is shaped as in Astacus astacus, but it is separated 

 from the body of the epistome by a transverse furrow. Length about 

 three inches. It would seem from Milne-Edwards's diagnosis and from 

 the same author's description and figure of Astacus aiistralasiensis 

 that, whatever Astacus cMlensis may prove to be, it is neither of the 

 two Chilean crayfishes described in this paper. In 1849, Mcolet' 

 described and figured as Astacus chilensis Milne-Edwards, a species of 

 crayfish found "in the rivers of Chile" — a species manifestly distinct 

 from Milne-Edwards's. For, not to mention other peculiarities, the 

 carpus is described and figured by Nicolet as furnished with a crest of 

 blunt, tuberculiform teeth on its inner border, whereas Milne-Edwards 

 distinctly says that there are neither teeth nor tubercles upon the carpus 

 of A. cMlensis. I therefore propose to call Nicolet's crayfish Parastacus 

 nicoletii (= Astacus chilensis Nicolet nee Milne-Edwards). 



Parastacus hassleri is similar to P. nicoletii. That both of them are 

 fossorial in their habits is evinced by the marked compression of the 

 cephalo-thorax, small size of the first abdominal segment, etc. The 

 following comparison will make clear the chief specific differences 

 between the two species : In P. nicoletii the anterior part of the sides of 

 the carapace is covered with fine spinules; in P. hassleri these spinules 

 are replaced by a small group of blunt tubercles. In P. nicoletii the ros- 

 trum does not overreach the proximal end of the second segment of 

 the antennular peduncle; it is quadrate in form, with straight and i)ar- 

 allel lateral margins, its upper surface deeply concave. In P. hassleri 

 the rostrum is longer, attaining almost to the distal extremity of the 

 second segment of the antennular peduncle; its upper surface is but 

 lightly hollowed out, while its lateral borders are distinctly convergent 

 from the base forward. The carpus of P. nicoletii is furnished with a 

 conspicuous crest of rounded, tuberculiform teeth along its inner supe- 

 rior border, and the outline of the opposite, lower or external border 

 is extremely convex or protuberant. In P. hassleri the tubercular 

 crest is obsolete, being represented merely by a few lightly pronounced 

 denticles; the lower or external border is but slightly convex, whereby 

 the carpus comes to have a triangular outline. Finally, the hand of 

 P. hassleri is much longer than that of P. nicoletii, its upper border 

 longer, straighter, and less strongly tuberculate, the fingers less deei)ly 

 sulcated. 



According to Nicolet, crayfishes are found in the rivers, brooks, and 

 even in the forests, of southern Chile, where they live in holes in the 

 ground, around the entrance of which they construct earthworks in 

 the shape of a cone nearly a foot in height. As is well known. Cam- 

 harus diogenes Girard, erects similar mud towers or " chimneys" in the 



'Gay's Historia Fisica y Politica de Chile, Zoologia, III, p. 211; Atlas, II, Crns- 

 tiiceos, pi. I, fift'. 4. 



Proc. ]Sr. M. vol. XX 44 



