212 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Remarks: Pisidia magdalencnsis seems to be completely absent from 

 the Gulf of California, although it appears commonly in shallow-water 

 dredge hauls throughout the rest of the Panamic Province. Records are 

 lacking for the region between the southern end of the Baja California 

 peninsula and White Friars Islands, which lie at about 17° 31' north 

 latitude. 



Range: Bahia de Santa Maria, Baja California, south to Bahia 

 de Santa Elena, Ecuador; absent from the Gulf of California. Shore to 

 25 fathoms. 



MEGALOBRACHIUM Stimpson 1858 



Megalobrachium Stimpson, 1858, p. 228 (type species Megalohrachiiwi 



granulifcrum Stimpson, 1858, by original designation). 

 Porccllanides Nobili, 1901b, p. 21 (type species Porcellanides festae 



Nobili, 1901, by monotypy). Preoccupied by Porcellanides Czer- 



niavsky, 1884. 

 Porcellanopsis Rathbun, 1910, p. 601 (type species Porcellanides festae 



Nobili, 1901, by monotypy ).'^ 

 Pisonella Glassell, 1938a, p. 436 (type species Petrolisthes (Pisosoma) 



sinuimaniis Lockington, 1878, by original designation). 



Carapace approximately as long as broad, strongly convex front 

 to back. Front prominent, trilobate to tridentate; strongly deflexed, the 

 teeth or lobes usually not visible in dorsal view. Outer orbital angles 

 not produced ; eyes usually very small, often not visible in dorsal view. 



Basal segment of antenna strongly produced forward and broadly 

 in contact with anterior margin of carapace, with movable segments 

 far removed from orbit; inner side truncate, not produced inward. 

 Movable segments slender. 



Basal segment of antennule very small, the two not meeting at the 

 midline, recessed behind front, latter projecting over them like a shelf; 

 a tooth sometimes present on inner side of anterior margin. 



Chelipeds large, often robust ; carpus and manus with longitudinal 

 ridges or strong tubercular protuberances. 



Walking legs variable in length, smooth to tuberculate; propodus 

 with movable accessory spinules on posterior margin ; dactylus ending 



1 "Porcellanopsis, new genus, for Porcellanides Nobili, 1901, preoccupied by 

 Porcellanides Czerniawsky, 1884 . . .". If Porcellanopsis is taken to be a substitute 

 name as Miss Rathbun apparently intended, rather than a new genus, the type 

 species is still Porcellanides festae Nobili. 



