84 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Petrolisthes galapagensis, new species 

 Plate 2 ; plate 25, fig. 2 



Petrolisthes eriomerus, Boone, 1932, p. 52, text-fig. 16. Not P. erio- 

 merus Stimpson. 



Previous records: Galapagos Islands. Bahia de Gardner, Isia 

 Hood: W. Beebe on A returns (Boone). 



Types: Holotype, male, U. S. National Museum Cat. No. 102403, 

 from Black Bight, Isla Albemarle, Galapagos Islands, rocky shore; 

 February 8, 1933; collected during Allan Hancock Pacific Epedition 

 of 1933 at Velero III station 62-33. Paratypes: 65 specimens from 

 the same and seven other stations (see Table 23). 



Diagnosis: Carapace subquadrate, its margins subparallel posterior 

 to epibranchial angle, nearly smooth ; no epibranchial spine ; front 

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

 margin unarmed, margins subparallel ; manus with a low crest on 

 outer margin; fingers blunt, often short and stubby; merus of walking 

 legs unarmed. 



Description: Carapace about as broad as long, subquadrate, lateral 

 margins nearly parallel behind epibranchial angle ; nearly smooth, 

 covered anteriorly with fine granules and posteriorly with light pli- 

 cations; grooves marking the various regions distinct. Frontal region 

 deflexed; front strongly produced, triangular, with a distinct median 

 groove extending to between protogastric lobes; no supraocular spine; 

 inner orbital angle not produced. Orbits rather shallow; outer orbital 

 angle only slightly produced. No epibranchial spine. Carapace naked. 



First movable segment of antennae faintly granular, with a low 

 crest on anterior margin ; second and third nearly smooth or faintly 

 granular, without anterior projections; flagellum naked or with vesti- 

 gial hairs visible only under magnification. Outer maxillipeds lightly 

 rugose. 



Chelipeds naked, finely granular dorsally, appearing almost smooth; 

 ventral surface smooth. Merus with a broad, low, rounded granular lobe 

 on anterior margin. Carpus one and a half to two times as long as 

 wide, margins subparallel; posterior margin with a low, obscurely 

 rugose crest scarcely produced distally, this crest defined by a narrow, 

 often obsolescent longitudinal groove. Manus flat, its outer edge with a 

 low, smooth crest extending onto pollex. Fingers blunt, curved at tips, 

 cutting edges without teeth; in one cheliped usually short, stubby, 



