326 INVERTEBRATA OF MASSACHUSETTS 



Genus PILUMNUS, Leach. 



PiLUMNus Harrisii, Gould. Carapax having three teeth 

 on each side ; front bilobate ; hands smooth. 



Carapax quadrilateral, narrowed backwards, rounded before, 

 rectilinear behind and at sides. On each side are three triangular 

 teeth ; eyes distant ; orbits oval, with a fissure over the centre ; 

 front divided by a fissure into two lobes. Surface very minutely 

 granulated, and hispid with very short, scattered hairs, which en- 

 tangle the dirt ; there are three or four broken series of curved, 

 transverse lines or ridges, rising into little crests. Limbs slender, 

 cylindrical. Carpus with a projecting angle in front. Hands ro- 

 bust, smooth, white within and without, and with a double line 

 along the upper edge ; finger deflexed and furrowed ; thumb also 

 furrowed and deflexed. The hands are generally unequal, and 

 the smaller one sometimes has elevated lines on its outer face. 

 Length j\ inch ; breadth half an inch. 



First found by Dr. T. W. Harris, on the Cambridge marshes ; 

 and not unfrequently seen, in summer, clinging to floating sea- 

 weed in Charles River. 



The sculpture of its margin and front, and the form and smooth- 

 ness of the hands, forbid tlie idea of its being the young of any 

 of our larger crabs. 



Genus HYAS, Leach. 



H. coarcta'ta. Carapax ovate, ivarty and hairy, narrowed 

 at the anterior third ; rostrum depressed, divided by a profound 

 fissure ; limbs short and small. 



Hyas coarctuta, Leach; Malac. Podoph. Brit., pi. 21 B. Milne-Edw.; Hist. 



Kat. des Crust., i. 312. Desji. ; Consid., 148. 

 Lissa fissiroslra, Say ; Juurn. .flcad. M'at. Sc, i. 79. 



This crab is an inhabitant of deep water, and is a favorite food 

 of the cod-fish, being very frequently found in its maw. I have 

 seen its exuviae in great quantities upon the outside of Cape Cod. 

 It is about two inches in length and somewhat less in breath, the 

 front projecting and divided by a fissure ; there is a notch a little 



