COMPLETE HAIG: EASTERN PACIFIC PORCELLANIDAE 119 



Remarks: This form has been found so far only on Isia del Coco, 

 an isolated island with a high degree of endemism in its fauna. 



Range: Isla del Coco, Costa Rica. 



Petrolisthes artifrons, new species 



Plate 7 ; plate 22, fig. 4 



Petrolisthes leivisi, Haig, 1957b, p. 7 (part). Not P. lewisi (Glassell). 



Previous records: 

 Panama. Guayabo Chiquito: Askoy (Haig). 

 Colombia. Bahia Limon, Golfo de Cupica: Askoy (Haig). 



Types: Holotype, male, U. S. National Museum Cat. No. 102407, 

 from south of Punta Santa Elena, Ecuador, rocky shore; January 18, 

 1933; collected during Allan Hancock Pacific Expedition of 1933 at 

 Velero III station 10-33. Paratypes: 197 specimens from the same 

 and 15 other stations (see Table 37). 



Diagnosis: Carapace nearly smooth, anterior regions and grooves 

 strongly accentuated; no epibranchial spine; front narrow, trilobate; 

 carpus about one and a half times as long as wide, proximal two-thirds 

 of anterior margin with a broad, strongly projecting lobe, its edge ob- 

 scurely divided into three; manus swollen on dorsal surface, with two 

 low longitudinal crests separated by a narrow groove, outer margin 

 with a crest defined by a distinct groove ; merus of walking legs un- 

 armed. 



Description: Carapace subpvate, margins posterior to epibranchial 

 angle not parallel ; covered with light plications except for metabranchial 

 regions, the latter smooth. Frontal groove and grooves defining the 

 various regions strongly accentuated. Carapace convex front to back; 

 front rather narrow, distinctly trilobate in dorsal view (sinuously tri- 

 angular in some small specimens), median lobe broad, rounded-triangu- 

 lar, strongly produced beyond eyes, lateral lobes narrower, rounded, 

 directed forward, less strongly produced than median lobe but extending 

 beyond eyes. Orbits rather shallow, obliquely concave; outer orbital 

 angle only very slightly produced. No epibranchial spine. Carapace with 

 a trace of hairs on frontal region in adults. 



Movable segments of antenna smooth to lightly granular, first with 

 a low crest on anterior margin, second and third without projections; 

 flagellum with scattered long hairs. Outer maxillipeds lightly rugose. 



