CAMBAEUS. 93 



(7. affinis, and more closely C. Pidnami ; but the young of the first may 

 be distinguished by the carinated rostrum ; of the second, by the longer 

 rostral acumen, antennal scale, and anterior spine of post-orbital ridge, by 

 the longer hand and internal carpal spine, and by the divergent tips of the 

 first pair of abdominal appendages in the male ; of the third, by the longer- 

 spined antennal lamina, and the long, deeply cleft abdominal appendages of 

 the male. 



In C. ohscuriis Hag., which I deem a local form of C. iwopinqims, the ros- 

 trum is somewhat broader, not carinate above, and less deeply hollowed out 

 than in the typical C propinqims ; the hand is broader, with a few tubercles 

 disposed in a longitudinal row opposite the base of the movable finger ; the 

 fingers are more widely separated at the base, the epistonia more truncate ; 

 the male appendages have a projecting angle or shoulder on the anterior 

 margin at the base of the rami, the outer part often grooved longitudinally 

 on the outer side. This form has been discovered only at Rochester, N. Y. 

 The differences between it and C. propinqims are so slight that I consider it 

 only a variety. Some specimens of C. propinqims show a strong tendency to 

 develop the projecting shoulder on the front border of the male appendages. 



In the United States National Museum is a small first-form male of a 

 Cambarus labelled "California" (No. 25.31), which I cannot distinguish spe- 

 cifically from C ohscuriis. The areolar part of the back of the carapace is 

 a little flatter, and the row of small tubercles on a line with the middle of 

 the base of the movable finger is not apparent ; but this often happens 

 in small specimens of C. obscurus. The locality of this specimen is very 

 probably erroneous, as no other specimen of a Cambarus from the Avest coast 

 is known. 



Hagen thinks that C. obscurus may be the Astacus fossor of Rafinesque. 

 Rafinesque's description is as follows : — 



" Astacus fossor. Antens length of the body, rostrum short, one-toothed 

 on each side, a thorn behind the eyes ; three pairs of pinciferous feet, hands 

 of the first pair very large, granular, gaping, toothed, with a furrowed and 

 bispinous wrist. — Obs. Vulgar name, burrowing lobster, — communicated to 

 me by Dr. Samuel L. Mitchill, — native of Virginia, Pennsylvania, and New 

 York ; size from four to six inches ; it burrows in meadows and milldams, 

 which it perforates and damages." 



It is impossible to determine what species is here meant. The descrip- 

 tion would suit C. projnnquus, a commoner form, as well as C. obscurus. 



