302 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



E. Chelipeds very unequal and dissimilar. 



F. Left cheliped the larger. Third maxillipeds approximate at base. 



Petrocliirus. 

 ' F'. Right cheliped the larger. Thirdmaxillipeds distant at base.. Pa^/wri/s. 

 E'. Chelipeds equal or subequal, and similar. 



F. Dactyli of second and third pairs of feet not twisted Clibana7'ius. 



F'. Dactyli of second and third pairs of feet twisted Isocheles. 



D'. A movable rostriform process between the eye stalks. Left cheliped the 



larger Diogenes. 



C Fifth leg of male on left side with an appendage at base. 



D. Appendage more or less spirally twisted Spii'opagurus. 



D'. Appendage short and curved Anapagurus. 



B'. First and second abdominal segments provided with genital appendages. 



Paguristes. 

 A'. Pleon composed of seven distinct segments Glaucotlioe, a larval form. 



Genus PETROCHIRUS Stimpson. 

 (Includes Pagurus Stimpson.) 



KEY TO THE WEST AFRICAN SPECIES OF THE GENUS PETROCHIRUS. 



A. Hands with an oval cavity on the upper surface near the inner margin . . cavitarius. 

 A'. Hands without an oval cavity on the upper surface near the inner margin. 

 B. Upper surface of propodus of large cheliped more or less spinous. 



C. Upper surface of propodus of large cheliped crossed obliquely by rough striae. 



D. StritB spinous only toward their inner side arrosor. 



D'. Striae spinous throughout their length arrosor pectinatus. 



C Upper surface of propodus of large cheliped with spines arranged partly in 



longitudinai rows pustulatus. 



B' Upper surface of propodus of large cheliped covered with small irregular 

 plates overlapping like tiles granuUmanus. 



PETROCHIRUS ARROSOR (Herbst) . 



Cancer arrosor Herbst, Natur. Krabben u. Krebse, II, 1796, p. 170, pi. xliii, fig. 1. 

 Pagurus strigosus Bosc, Hist. Nat. Crust., II, 1802, p. 77, pi. xi, fig. 3. 

 Pagurus striatus Latreii.le, Hist. Kat. Crust., VI, 1803, p. 163. 



The type of this species is preserved in the Berlin Museum. 



Range. — Mediterranean; Portugal; West Africa, including islands; 

 Japan (de Haan); Zebu, Philippines (Henderson); off Tablas Island, 

 100 to 115 fathoms (Henderson). 



West African localities. — Madeira (Stimpson, Miers, Studer); Cape 

 Yerde Islands, 47 fathoms (Studer); Goree Bay, Senegambia, 9 to 15 

 fathoms (Miers); Dakar to 8 meters, Goree, 15 meters, aud Eufisque, 6 

 meters (Chevreux and Bouvier). 



PETROCHIRUS ARROSOR PECTINATUS Ortmann. 



Pagurus sMatus var. peetinata Ortmann, Zool. Jahrb., Syst., VI, 1892, p. 284, 

 pl. XII, fig. 10. 

 Range. — Brazil (Ortmann); Dakar, Senegal (O. F. Cook, collector). 

 In this form, which may prove to be a distinct species, the last two 

 joints of the third foot of the left side have a longitudinal median sulcus 

 on the outer surface much deeper than in any specimens of typical P. 

 arrosor. 



