COMPLETE HAIG : EASTERN PACIFIC PORCELLANIDAE 175 



chelipeds; by the carpal lobe with its margin nearly entire; and by the 

 long, scattered plumose hairs which decorate the chelipeds. P. holo- 

 sericus is also related to the west African species P. bellus (Osorio), 

 as defined by Chace (1956, p. 11, text-fig. 3). In that species, which 

 like P. holosericus has a five-plated telson and male pleopods, the manus 

 is more swollen and tuberculate than in the eastern Pacific form and 

 there are long plumose hairs on the manus of the minor cheliped in addi- 

 tion to the short pile covering its surface. 



Range: Santa Barbara, California, south to Bahia de la Magdalena, 

 Baja California. 



CLASTOTOECHUS, new genus 

 Type species: Petrolisthes diffractus Haig, 1957. 



Carapace rounded, approximately as broad as long ; upper surface 

 rough, uneven. Side walls incomplete, the posterior portion consisting 

 of many very small fragments separated by narrow membranous inter- 

 spaces. Front strongly produced, distinctly trilobate. Eyestallcs short 

 and stout, retractile. 



Basal segment of antenna not produced forward to meet anterior 

 margin of carapace; with a small inward projection. Movable segments 

 somewhat nodulate. 



Basal segment of antennule with three strong, lamellate, anterior 

 lobes. 



Chelipeds large, flattened, subequal but with fingers sometimes dif- 

 fering in the two chelipeds; carpus longer than broad, its anterior mar- 

 gin armed with prominent teeth. 



Walking legs of moderate length, somewhat flattened ; propodus 

 with movable spinules on posterior margin ; dactylus ending in a sim- 

 ple spine, with small, movable, accessory spinules on posterior margin. 



Telson of abdomen composed of five plates. 



Contains three species, one from Pacific and two from Atlantic 

 America. 



Remarks: This genus is proposed for the reception of two western 

 Atlantic species, Petrolisthes nodosus Streets, 1872, and P. vanderhorsti 

 Schmitt, 1924, and an eastern Pacific species, P. diffractus Haig. The 

 form of the front, side walls of the carapace, carpus of the chelipeds, 

 and basal segment of the antennules (text-fig. 5), together with the 

 five-plated telson, are characters warranting generic distinction. 



