COMPLETE HAIG: EASTERN PACIFIC PORCELLANIDAE 81 



it is shown in Plate 27, fig. 2 and in the specimen illustrated by Stein- 

 beck and Ricketts (1941, pi. 29, fig. 4). 



Ecology: Petrolisthes gracilis is almost strictly a littoral species; 

 Hancock Foundation collectors took it from under stones at all stations 

 but one, where it was recovered from coral. It was dredged by the 

 Velero III on two occasions: in 10 fathoms from a bottom of sand and 

 rock, and in 18-25 fathoms from a sand bottom. 



Ovigerous females have been collected in every month from January 

 through June. 



Remarks: Although Stimpson's description of Petrolisthes gracilis 

 was unsatisfactorily brief and his type specimen is no longer extant, the 

 Gulf of California type locality is sufficient to identify the species; no 

 other Petrolisthes with which it might be confused occurs in the Gulf. 

 P. gracilis is a Gulf of California endemic and, like some other Gulf of 

 California endemic species, is established at the southern end of the outer 

 Baja California coast and on the Tres Marias Islands. The Velero III 

 record from Bahia Tangola-Tangola should be accepted with caution, 

 pending additional recoveries of the species along the Mexican main- 

 land south of the Gulf of California. California specimens identified 

 with P. gracilis by Schmitt (1921) belong to a distinct species, P. 

 rnanimaculis Glassell ; Nobili's (1901b) Ecuador record was based on 

 P. tridentatus Stimpson. 



Range: Bahia de Santa Maria, Baja California; Gulf of California, 

 from Punta Pefiasco and San Felipe south to La Paz; Islas Las Tres 

 Marias. Extralimital : Bahia Tangola-Tangola, Mexico. Shore; rarely 

 to 25 fathoms. 



Petrolisthes tridentatus Stimpson 



Plate 25, fig. 4 



Restricted synonymy: 



Worcellana affinis Gray, 1831, p. 15 (type locality unknown). H. 



Milne Edwards, 1837, p. 257. White, 1847, p. 63. 

 Petrolisthes tridentatus Stimpson, 1858, p. 227 (listed only; type local- 

 ity, Antilles) ; 1859, p. 75, pi. 1, fig. 4 (description; type localities 

 restricted to Barbados and St. Thomas). Schmitt, 1935, pp. 185, 

 187, text-fig. 47. Haig, 1957b, p. 8. 

 Petrolisthes gracilis, Nobili, 1901b, p. 13. Not P. gracilis Stimpson. 

 Petrolisthes eriomerus, Boone, 1931, p. 154 (part), text-fig. 8. Not 

 P. eriomerus Stimpson. 



