108 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Petrolisthes platymerus, new species 

 Plate 4; plate 29, fig. 3 

 Petrolisthes eriomerus, Boone, 1931, p. 154 (part). Not P. erio- 

 ffierus Stimpson. 



Previous records: Panama. Isla Taboguilla: W. G. Van Name 

 (Boone). 



Types: Holotype, male, U. S. National Museum Cat. No. 102405, 

 from Port Parker, Costa Rica, shore ; February 9, 1935 ; collected 

 during Allan Hancock Pacific Expedition of 1935 at Velero III sta- 

 tion 466-35. Paratypes: same data as holotype, three males, three fe- 

 males (two ovigerous), one young (U. S. National Museum); two 

 males, three ovigerous females (Allan Hancock Foundation). Para- 

 type: north shore of Isla Taboguilla, Panama, shore; March 4 or 5, 

 1926; collected by W. G. Van Name and Mrs. S. E. Brewster; one 

 female (American Museum of Natural History Cat. No. 6197). 



Diagnosis: Carapace rough and uneven, regions distinct and de- 

 fined by deep grooves; no epibranchial spine; front broad, sinuously 

 triangular; carpus one and a half to nearly two times as long as wide, 

 anterior margin unarmed, margins subparallel or very slightly converg- 

 ing distally ; manus somewhat swollen on dorsal surface, outer margin 

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

 unarmed, that of leg 3 broad, inflated. 



Description: Carapace rough, uneven, the regions distinct, those on 

 anterior half of carapace especially well defined by deep, broad grooves; 

 lateral areas posterior to cervical groove with small scattered tubercles. 

 Front broad, sinuously triangular, inner orbital angle somewhat pro- 

 duced; no supraocular spine; a deep median sulcus extending between 

 protogastric lobes. Orbits deep, angular, outer orbital angle produced 

 into a strong, narrow tooth. No epibranchial spine. Carapace covered 

 with a short, sparse pubescence. 



First movable segment of antenna with a low lamellar lobe on an- 

 terior margin; second granular, slightly produced at proximal and dis- 

 tal ends of anterior margin; third nearly smooth; flagellum with vesti- 

 gial hairs visible only under magnification. Outer maxillipeds lightly 

 rugose. 



Merus of chelipeds covered with small rough granules, anterior 

 margin with a small lobe. Carpus one and a half to slightly under two 

 times as long as wide; a distinct longitudinal crest about the center of 

 dorsal surface, and an obliquely rugose crest along posterior margin, 



