1905.] 



NATURAL SCIENCES OF PHILADELPHIA. 



371 



DESCRIPTION OF A NEW SPECIES OF COMMENSAL CRAB. 



BY MARY J. RATHBUN. 



The crab here described as new was submitted to me for determi' 

 nation by Dr. H. A. Pilsbry. It 

 differs from other American spe- 

 cies in its great breadth, and in the 

 form of the maxillipeds, the carpal 

 and propodal segments of which 

 are unusually short. 

 Pinnotheres strombi sp. nov. 



Description of adult 9 . — Carapace 

 nearly one and a half times as broad 

 as long, oblong, sides parallel, cor- 

 ners rounded; dorsal surface curv- 

 ing down toward the margins, 

 smooth and naked; integument 

 very thin and easily wrinkled. 



Front less than one-fourth width 

 of carapace, strongly bent down, P. strombi. Dorsal and ventral views 

 margin forming an oblique angle at ^^P^' + > ^ ^• 



middle. 



Orbits suborbicular, eyes partly visible in dorsal view. 



Antennules nearly horizontal. 



Outer maxillipeds oblique, the penult 

 and antepenult joints short and stout, the 

 last joint small and almost terminal. 



Chelipeds small, rounded ; upper margin 

 of propodus convex, lower margin sinuous; 

 fingers deflexed, about half as long as palm, 

 stout, fitting close together, tips sharp and 

 crossing. 



Second pair of ambulatory legs a little 

 the longest, first pair stoutest, fourth pair 



much shorter and narrower than the other three. Dactyli short, 

 strongly curved, stout at base, tapering to slender horny tips. 



Abdomen as wide as carapace, and about as long as wide. 



Outer maxilliped, much en- 

 larged 



