COMPLETE HAIG : EASTERN PACIFIC PORCELLANIDAE 197 



margins. Front prominent, strongly tridentate in dorsal view. Orbits 

 deep ; eyestalks stout, retractile. 



Basal segment of antenna strongly produced inward, forming a 

 partial suborbital margin and partly visible in dorsal view; produced 

 forward and broadly in contact with anterior margin of carapace, 

 with movable segments removed from orbit. 



Basal segment of antennule with strong anterior projections, usu- 

 ally partially visible in dorsal view. 



Chelipeds large, usually somewhat compressed ; fingers normal, not 

 twisted out of plane with palm. Propodus of walking legs usually with 

 posterior spinules; dactylus ending in a simple spine, usually with sev- 

 eral movable accessory spinules. 



Remarks: The old genus Porcellana as restricted by Stimpson 

 (1858) is a heterogeneous group which needs a thorough revision; 

 the species currently included in it should probably be allocated to at 

 least four distinct genera. In this report one group of species is trans- 

 ferred to Pisidia; aside from this no attempt is made to split Por- 

 cellana because the atypical species inhabit territory outside the scope 

 of this paper. In the opinion of the writer, the genus should be limited 

 to forms closely related to the type species, Porcellana platycheles 

 (Pennant), 1777, and having the combination of characters enumerated 

 above. In addition to the eastern Atlantic type species the genus would 

 then include Porcellana say ana (Leach), 1820, P. sigsbeiana A. Milne 

 Edwards, 1880, and P. frontalis Heller, 1862, western Atlantic; P. 

 pulchra Stimpson, 1858, western Pacific; and P. hancocki, P. paguri- 

 conviva, and P. cancrisocialis, all eastern Pacific species described by 

 Glassell. 



Porcellana corbicola, described herein, has several atypical features 

 including chelipeds much like those of Porcellanella White, 1852, and 

 walking legs without movable spinules on the lower margins of propodus 

 and dactylus. Nothing is known of its affinities at present, and until 

 the Porcellanidae as a whole can be revised it is tentatively placed in 

 Porcellana. 



Key to the Eastern Pacific Species 

 la. Fingers opening vertically; telson of abdomen with 5 plates 



corbicola 



lb. Fingers opening horizontally or somewhat obliquely; telson of 



abdomen with 7 plates 2 



2a. Lateral margin with a deep, narrow notch at cervical groove; 



manus slender, its surface somewhat swollen . . hancocki 



