merus and ischium of which are subquadrilateral, the palpus articu- 

 lating at the external angle of the former. 



Chelipeds shorter than legs, very unequal, the larger one stouter 

 than the legs. Chelae flattened ; palm short and high and bearing on 

 the inner surface a stridulating ridge which can be scraped against 

 a corresponding ridge on the ischium. 



Legs broad, the fourth pair much shorter and slenderer than the 

 others, which are nearly equal. Between the basal joints of the 

 second and third pairs, is an orifice, thickly protected by hairs, lead- 

 ing toward the branchial cavity. 



Abdomen composed of seven segments in both sexes. 



Tropical and subtropical coasts, from the American Atlantic 

 (Rhode Island to Brazil), through the Mediterranean and Red Seas, 

 to the American Pacific (Lower California to Chile). 



Analogous species on opposite sides of the continent: albicans 

 (Atlantic); occidentalis (Pacific). 



KEY TO THE AMERICAN SPECIES OP THE GENUS OCTPODE. 



A 1 . Eyestalks not prolonged beyond the eyes in the form of a style. Fingers 



pointed. 



B 1 . Orbital angles distinctly less advanced than the front. Merus of an- 

 bulatory legs hairy __________________________________ albicang, p. 367. 



B 2 . Orbital angles as advanced or nearly as advanced as the front. Merus 

 of ambulatory legs naked _________________________ occidentalis, p. 372. 



A 1 . Eyestalks prolonged beyond the eyes in the form of a style. Fingers 

 truncate __________________________________________ gaudichaudii, p. 373. 



SPECIES ERRONEOUSLY REPORTED AS AMERICAN. 



O. macrocera MILNE EDWARDS. Recorded from Brazil in Hist. Nat. Crust., 

 vol. 2, 1837, p. 49, but not in later work. Ann. Sci. Nat., Zool., ser. 3, 

 vol. 18, 1852, p. 142 [106]. 



OCYPODE ALBICANS 



SAND CRAB ; GHOST CRAB. 



Plates 127 and 128. 



Cancer arenarius CATESBY, Nat. Hist. Carolina, vol. 2, 1743, p. 35, pi. 35, 

 " Ilathera, and many others of the Bahama Islands." 



Cancer vocans LINNAEUS, Syst. Nat., ed. 10, vol. 1, 1758, p. 626 (part). 



Cancer quadratus FABHICIUS, Mant. Ins., vol. 1, 1787, p. 315 (type-locality, 

 Jamaica; type examined In Copenhagen Mus.) ; Ent. Sys., auct. et 

 emend., vol. 2, 1793, p. 439 ; not C. quadrata Meuschen, 1781. 



Ocypode quadrata FABKICIUS, Ent. Syst., Suppl., 1798, p. 347. 



t Ocypode rhombea FABBICIUS, Ent. Syst., Suppl., 1798, p. 348 ; locality not 

 known. 



Ocypoda albicans Bosc, Hist. Nat. Crust., vol. 1, an X [1801-1802], p. 196, 

 not pi. 4, fig. 1 (type-locality, la Caroline; type not extant). 



