26 ALLAN HANCOCK ATLANTIC EXPEDITION REPORT 



Remarks. — Known from shore to 20 fathoms; taken in Pontes and 

 gorgonian coral and in sponges. 



Rathbun (1900) considered PetroUsthes serratus Henderson to be 

 probably identical with P. arnoenus. 



Boone (1932, p. 41, text-figs. 11-12) reported PetroUsthes arnoenus 

 from the Galapagos Islands; however, her description and figure of an 

 adult do not agree with this species. The writer has seen a note by S. A. 

 Glassell, stating that Boone's specimens belong to one of his undescribed 

 species. 



Petrolisthes marginatus Stimpson 



PetroUsthes marginatus Stimpson, 1858, p. 227 (nomen nudum) ; 1859, 

 p. 74 (type locality, Barbados). Young, 1900, p. 394. Benedict, 

 1901, p. 134, pi. 3, fig. 1. Schmitt, 1924a, p. 73; 1924b, p. 88; 

 1935, pp. 185, 187. Not Nobili, 1897, p. 4, fide Nobili, 1901, 

 p. 12. 

 PetroUsthes galathinus Boone, 1932, p. 45 (not text-fig. 13; perhaps 



not text-fig. 14). Not P. galathinus (Bosc). 

 ^PetroUsthes galathinus Hult, 1938, p. 10. Not P. galathinus (Bosc). 



Previous records. — 

 Puerto Rico, Ponce: Fish Hawk (Benedict). Barbados: T. Gill (Stimp- 

 son, 1859); Univ. Iowa Barbados-Antigua Exped. (Schmitt, 1924b). 

 Curagao: C. J. van der Horst (Schmitt, 1924a). 



Material examined. — 

 A46-39. Vista Alegre, Curagao; Apr 23, 1939; shore. l$ov. 

 A41-39. Buccoo Reef, Tobago Island; Apr 20, 1939; shore. \d. 



Measurements. — Male, 14.5 mm; ovigerous female, 5.7 mm. 



Remarks. — This species is littoral and has been taken under stones 

 and in coral heads. 



In addition to the records given above, Petrolisthes marginatus has 

 been reported from the following Pacific localities: Isla Flamenco, 

 Panama, and Bahia de Santa Elena, Ecuador (Nobili, 1901), and 

 Clipperton Island (Schmitt, 1939). The writer has examined a number 

 of specimens collected by Velero III in Costa Rica, Colombia, Panama, 

 and the Galapagos Islands. 



In the Crustacea laboratory of the Hancock Foundation is a copy 

 of Boone (1932) originally owned by S. A. Glassell, and with hand- 

 written annotations made by him. According to Glassell's notes, the 

 Galapagos Islands material identified by Boone as Petrolisthes gala- 

 thinus is actually P. marginatus. Boone's description (pp. 46-48) fits 



