70 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Petrolisthes tiburonensis Glassell 

 Plate 25, figs. 1, 3 



Petrolisthes tiburonensis Glassell, 1936, p. 284 (type locality, S end 

 of Isla Tiburon, Gulf of California) ; 1938a, p. 444. 



Previous records: Gulf of California. Puerto Refugio, Isla Angel 

 de la Guarda; Bahia de los Angeles; S end Isla Tiburon: S. A. 

 Glassell (Glassell 1936). 



Diagnosis: Carapace with rough granules and plications, raised 

 into rough transverse ridges ; no epibranchial spine ; front sinuously 

 triangular, with a strong conical tubercle at tip and one on either 

 side; carpus in males over three times as long as wide, anterior 

 margin unarmed, margins subparallel; carpus in females and young 

 about two and a half times as long as wide, anterior margin with a row 

 of spinules, margins slightly converging distally; manus with a broad 

 median longitudinal crest, outer margin unarmed in males, spinulose 

 in females and young; merus of walking legs nodulose on anterior 

 margin, unarmed at posterodistal angle. 



Description: Carapace covered with rough granules and plications, 

 regions well marked and separated by deep grooves; in females and 

 young, especially, the plications raised into rough transverse ridges. 

 Front sinuously triangular, with a distinct median groove; its margin 

 with three well separated, strong conical tubercles, one at tip and one 

 on either side half way between it and inner orbital angle; these tuber- 

 cles more distinct and strongly projecting in females and young. Outer 

 orbital angle produced into a small tooth. No epibranchial spine. Cara- 

 pace naked in males, pubescent in females and young. 



First movable segment of antenna with a strongly projecting, nodu- 

 late lobe; second and third nodulate, most markedly so in females and 

 young ; flagellum naked or with vestigial hairs visible only under magni- 

 fication. Outer maxillipeds lightly rugose. 



Chelipeds covered with fine granules. Merus with a low granular 

 lobe on anterior margin. Carpus in males over three times as long as 

 wide, margins subparallel; anterior margin unarmed; dorsal surface 

 with a low longitudinal crest ; posterior margin with a low crest covered 

 with slightly enlarged granules, and ending distally in a small tooth. 

 Carpus in females and young about two and a half times as long as 

 wide, margins slightly converging distally; anterior margin armed 



