COMPLETE HAIG : EASTERN PACIFIC PORCELLANIDAE 121 



Remarks: Petrolisthes artifrons occupies much the same range as 

 P. leivisi austrinus, new subspecies, and the two forms often occur to- 

 gether. 



The name artifrons is from the Latin artus, narrow, and frons, 

 forehead, in reference to the narrow front characteristic of this species. 



Range: Port Parker, Costa Rica, south to Punta Santa Elena, 

 Ecuador. 



Petrolisthes hians Nobili 

 Plate 22, fig. 3 



Petrolisthes hians Nobih', 1901b, p. 17 (type locality, Bahia de 

 Santa Elena, Ecuador). Rathbun, 1910, p. 599. Haig, 1957b, p. 7. 



Pisosoma flagraciliata Glassell, 1937, p. 82, pi. 1, fig. 2 (type local- 

 ity, off Arena Bank, Gulf of California). Steinbeck and Ricketts, 

 1941, p. 458. 



Previous records: 



Gulf of California. Off Arena Bank: W. Beebe on Zaca (Glassell). 

 Pulmo Reef; Cabo de San Lucas: J. Steinbeck and E. F. Rick- 

 etts (Steinbeck and Ricketts). 



Colombia. Bahia Humboldt: Askoy (Haig). 



Ecuador. Bahia de Santa Elena: E. Festa (Nobili). 



Diagnosis: Carapace nearly smooth, anterior regions and grooves 

 strongly accentuated ; no epibranchial spine ; front trilobate, the median 

 lobe very narrow; carpus less than one and a half times as long as 

 wide, anterior margin with three or four broad rounded teeth; 

 manus with a crest on outer margin, defined by a distinct groove; 

 merus of walking legs unarmed ; telson of abdomen with five plates. 



Description: Carapace covered with rough plications anteriorly, 

 smooth or punctate posteriorly ; protogastric, hepatic, and epibranchial 

 regions, and the grooves defining them, strongly accentuated. Frontal 

 region deflexed ; front broad, trilobate, lateral lobes broad and sinuate, 

 median lobe narrow, only slightly projecting beyond them. Outer or- 

 bital angle produced into a small, strong tooth. No epibranchial spine. 

 Carapace devoid of hairs. 



First movable segment of antenna with two minute spinules on an- 

 terior margin ; second with a minute spinule on anterior margin at 

 distal end, and often one at proximal end as well ; third without an- 

 terior projections ; flagellum with long hairs. Outer maxillipeds rugose. 



