COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 115 



on the margins are a little stronger than those on the middle; strong 

 imbricating lamellae cross the ribs. The anterior ear is ornamented by 

 about six to seven imbricated riblets and the posterior shows about five 

 such riblets. The exterior of the shell is colored pink vi^ith whitish and 

 brownish spots. The hinge line has transverse striations; the ribs are 

 shown on the interior of the shell by strong ridges and hollows. Other 

 specimens sometimes have pairs of raised ribs instead of only one. Type, 

 altitude approximately 6.4 mm. ; length of hinge line approximately 6.2 

 mm. 



Additional descriptive notes: The right valve is moderately convex, 

 the left flattish. Every third rib of the left valve is angular and has 

 prominent concentric lamellae, the other ribs being rounded and much 

 smoother ; one or two riblets are present in the interspaces. On the right 

 valve a low central riblet (rarely two) occurs between the major ribs, 

 both the ribs and interspaces being concentrically lamellated ; a well- 

 defined byssal notch is present and a ctenolium of five teeth ; the anterior 

 auricle has five imbricated riblets, the posterior five or six. The left valve 

 is pink, red, or red-brown, with white and brown markings ; the right 

 valve is either much paler than the left or white. Fully grown specimens 

 attain an altitude of 16 or 17 mm. 



Geographical range'. Las Animas Bay, Gulf of California, to Puna, 

 Gulf of Guayaquil, Ecuador. Mazatlan, Mexico, was the previously 

 recorded northern limit, but specimens in the author's collection from 

 Las Animas Bay extend the range by about 570 miles. 



Geochronological range: Reported only from the Recent. 



Bathymetric range: Recorded in 3 to 40 fathoms. 



Ecological data: Found on rock, gravelly sand, sand, and mud bot- 

 toms. 



Hancock Expeditions Collecting Stations: 

 ECUADOR: La Libertad, 3-5 fathoms, sand, sta. 9-33 and bottom 

 sample 504; Santa Elena Bay, 8-10 fathoms, rock, sta. 209-34. 



Chlamys (Leptopecten) velero biolleyi (Hertlein & Strong) 1946 



Plate 38 



Pecten (Leptopecten) velero biolleyi Hertlein & Strong, 1946, p. 60, 

 pi. 1, fig. 6. ". . . dredged in 12 fathoms (22 meters) in Lat. 10° 

 55' 45" N., Long. 85° 49' 05" W., Port Parker, Costa Rica, on 

 bottom of sandy mud and crushed shells." — Hertlein Si, Strong, 

 1955, p. 181. ". . . Guayabo Chiquito Bay, Panama, . . . 25-64 

 meters, . . . gray mud bottom." 



