108 PEOCEEDINGS OF THE AMERICAN ACADEMY 



all the Crayfishes found in the Northern hemisphere, viz. the family 

 PotamohiidcB of Huxley. Owing to unavoidable delay in the jiubli- 

 cation of the full Revision in the Memoirs of the IVIuseum of Com- 

 parative Zoology, illustrated by quarto lithographic plates, it is thought 

 advisable to jiublish the following descriptions of the new species. 

 All of them will be figured in the final Memoir. 



Genus CAMBARUS. 



§ 1 . Third and fourth pairs of legs of male furnished with hooks on 

 the third segment. First abdominal appendages of the male with 

 outer part truncate at the tip and furnished with one to three small 

 recurved teeth, inner part ending in an acute spine which is gen- 

 erally directed outwards. 



a. Rostrum with ante-apical lateral spines. 



1. C. Hayi, sp. nov. 



Male, form I. Rostrum broad, triangular, excavated, sparsely 

 pubescent above, acumen short, lateral spines moderate. Carapace 

 punctate above, granulated on the sides, the granules ciliate. Lateral 

 spines slightly developed in fully-grown individuals, more prominent 

 in the young. Areola narrow. Abdomen broad, shorter than the 

 cephalo-thorax. Pleural angles rounded. Proximal segment of telson 

 with two spines on each side of the distal border. Hind margin of 

 telson slightly concave. Anterior process of epistoma broadly tri- 

 angular. Antennfe shorter than the body. Antennal scale a little 

 shorter than the peduncle, equal to the rostrum, broad, broadest at the 

 middle. Chelipeds slender, chela long, inner and outer margins paral- 

 lel, squamoso-tuberculate, tubercles ciliate, those along the inner 

 margin of the hand blunt spiniform. Fingers longer than the hand. 

 Opposed margins of fingers ciliate, with one or two small spinous 

 teeth. Carpus long triangular, smooth without, tuberculate and 

 spinous within. Meros with scattered puncta without, tuberculate on 

 the upper margin, one or two spines at the anterior end of upper 

 margin, two rows of spines beneath. Third and fourth pairs of legs 

 hooked on tliird segments. Anterior abdominal legs of moderate 

 length, deeply excavated on the outer side near the tip. A beard- 

 like tuft of cilia from the protuberance behind the excavation. Tip 

 bears three flattened horny teeth. Inner part ciliate, with a long 

 spine directed outwards and forwards. 



The second form of the male has shorter chelipeds, smaller hooks 



