COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 105 



inent from ventral margin nearly to unbonal area. Both auricles covered 

 with concentric striae and having 7 or 8 low ridges; anterior auricle 

 with shallow byssal sinus, posterior same shape as that of right valve. 

 Cardinal crura fairly strong to very strong; crura and provinculum 

 black or very deep brown except in yellow-white or white specimens, in 

 which that area is white; heavy nodule at base of each auricle. Rest of 

 internal structure unique after shell attains height of about 75 mm: 

 broad and flat semicircular ridge forms in each valve, reaching from 

 anterior to posterior submargin ; top edge of ridge is about two-thirds to 

 three-quarters of distance from hinge line to ventral margin ; ridge is 

 thickest in its center and tapers above and below. Color range fairly 

 extensive: most common form white with purple ribs, variants having 

 ribs of pink, pink and purple or pale to deep brown, often mottled ; less 

 common colors solid orange, yellow-white, white, and orange mottled 

 with purple-brown and white. Interior with prominent concentric band 

 of brown, purple-brown, purple or violet, except in yellow-white or 

 white specimens, which have white interior. 



Remarks'. Although somewhat variable, this species is very distinct 

 and easily recognizable. On the basis of available material the maximum 

 length appears to be about 150 mm. 



Lamarck's report of this species from Japan was obviously erroneous. 



Geographical range: Corinto, Nicaragua, to Coquimbo Province, 

 Chile. 



Geochronologtcal range: Pliocene, Pleistocene, Recent. 



Bathymetric range: Shallow water inshore to 50 fathoms. 



Ecological data: Found on rock, shale or sand bottoms, occasionally 

 associated with algae. 



Hancock Expeditions Collecting Stations: 

 PERU: 8 stations; one each at Lorenzo and Fronton Islands, near 



Callao, six in Independencia Bay; 5-10 fathoms, rock or sand. 

 COSTA RICA: Port Parker; 5 fathoms, sand, sta. 468-35. 



Subgenus LEPTOPECTEN Verrill 1897 



Leptopecten Verrill, 1897, p. 69. Type species (by monotypy) : Pecten 



Monotimeris Conrad, 1837, p. 238, pi. 18, fig. 10 [= Chlamys 



(Leptopecten) latiaurata monotimeris (Conrad)]; type locality: 



San Diego, California. 



Original diagnosis: Shell thin, translucent, oblique, broadly rounded, 



with strong, rounded radial ridges or folds, like corrugations, which 



