264 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



Genus HEMIGRAPSUS Dana. 



Hemigrapsus DANA, Amer. Journ. Sci., ser. 2, vol. 12, 1S51, p. 288 ; Proc. 

 'Acad. Nat. Sci. Philadelphia, vol. 5, 1851 (1852), pp. 247 aiid 250; 



type, H. crassimanus Dana. 

 LobOf/rapswi A. MILNE EDWARDS, Ann. Soc. Entora. France, ser. 4, vol. 9, 



1SG9, p. 173; type, L. crenulatus (Milne Edwards). 



Carapace broader than long, quadrate with the antero-lateral 

 margins rounded and dentate; depressed; an oblique ridge runs 

 inward and backward from the postero-lateral margin. Front less 

 than half width of carapace. Orbits of moderate size. 



Antennules folding obliquely. Tooth at inner angle of orbit well 

 developed. Antenna filling the orbital hiatus; flagellum entering the 

 orbit. The suborbital crest forms a tuberculated or striated stridu- 

 lating ridge which scrapes against the distal end of the arm. Epi- 

 stome well developed. 



Buccal cavity quadrate with the anterior corners rounded. Outer 

 maxillipeds moderately gaping; merus broader but very little shorter 

 than the ischium, and as broad as, or broader than long; its inner 

 and outer margins convex, anterior margin excavate, with the palpus 

 inserted toward its outer angle. 



Chelipeds equal or subequal, stout. Palms often with a patch of 

 hair inside. Fingers hollowed out beneath in a shallow groove. 



Legs of moderate length, and almost unarmed. 



The abdomen of the male does not cover the sternum at its base. 



Distribution. Temperate shores of the Pacific Ocean; Hawaiian 

 Islands; South Atlantic coast of America. 



KEY TO THE AMERICAN SPECIES OF THE GENUS HEMIGBAPSUS. 



A*. Three lateral teeth behind the orbital angle afflnis, p. 204. 



A*. Two lateral teeth behind the orbital angle. 



B 1 . Postero-lateral margins strongly convergent. Legs with thick fringes of 



hair crenulatus, p. 260. 



B'. Postero-lateral margins not sensibly convergent. 



C 1 . Legs devoid of hair. Two deep sinuses in the epistome nudus, p. 207. 



C*. Legs more or less hairy. Two shallow sinuses in the epistoine. 



orcgonensis, p. 270. 



HEMIGRAPSUS AFFINIS Dana. 



Plate 07. 



Hemigrapsus afflnis DANA, Proc. Acad. Nat. Sci. Philadelphia, vol. 5, 1851 

 (1S52), p. 250 (type-locality, Porto. 'Rio Negro' Patagoniac; type not 

 extant) ; U. S. Expl. Exped., vol. 13, Crust., pt. 1, 1852, p. 350; atlas, 

 1855, pi. 22, fig. 5. 



Diagnosis. Small, narrow; three side teeth f upper surface of 

 palm flattened; fingers subacute; sixth segment of male abdomen 

 shorter than fifth. 



