52 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



most a saflfron color in some pectens. The valves are marked 

 with zigzag stripes or mottled with a variety of shades of color. 

 Dark red with pink and reddish brown and yellow and yellowish 

 brown in varying shades are the prevailing colors. White shells 

 generally show reddish brown clouds and color markings and 

 shells with yellowing tints are marbled with yellowish brown. 

 The under or right valve is uniformly of a lighter color — 

 sometimes almost white. Occasionally a white valve with 

 yellow color markings will be joined to a valve with reddish 

 brown color marks, in fact, variety in color effects is one of the 

 great charm of the species. The color variation is so noticable 

 that the writer, in making a limited statistical study of the ribs 

 in a given number of specimens, also listed color variations in or- 

 der to make a comparative study. . A partial study was made of 

 four lots of shells collected respectively in the years 1893, 1894, 

 1897 and 1901 . The first named were collected by a fisherman 

 in Alamitos Bay (this is the extreme southern portion of the 

 larger bay San Pedro, but is locally called Alamitos Bayj. The 

 collection of 1894 was made by the writer. These pectens were 

 collected on a mud-flat on East San Pedro, on the channel side 

 of the bay. The pectens — extra large — of the 1897 ^^^ were 

 dredged in sand by a fisherman in San Pedro Bay, as was also 

 the lot of 1901, which was dredged by Mr. H. B. Torrey for use 

 in his class in the marine biological laboratory at East San Pedro= 

 Colors on the upper valve show more tendency to uniformity 

 than tints on the lower ones, being much darker as a rule. Colors 

 on lower valve, pure white, white mottled or marbled with red- 

 dish brown, saffron yellow, saffron mottled with brown; occasion- 

 ally a dirty grey with a few dashes of white but this color is 

 more generally represented on the upper valve. 



Pecten {Plagiocteninin) aequisulcatus Cpr. are sand dwellers, 

 In San Pedro Bay they are dredged in water from 4 to 14 feet, 

 but at very low tide, when a long stretch of wet sand lies un- 

 covered by the water, before the morning sun breaks his way 

 through the misty fog, a colony of scallop shells may be found in 

 a sandy mud flat. In this mud flat there are numerous little de- 

 pressions and in these, covered with water, Pecten aequisulcatus 

 are seen opening and shutting their valves so rapidly one hears 

 the sound in every direction, and, at the same time the scallop 

 throws out a stream of water while occasionally one of the seal- 



