38 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



the interstices of this granular layer. These greenish (?) white 

 bodies or spermatazoa are grouped into irregular masses of lace- 

 like layers on either side of the liver.* (fig. 5, plate iv.). 



The statistical tables are given merely to approximate variation 

 of the San Pedro scallops, not as conclusive proof of the variation 

 of species in form and color in that bay. 



The color given is the basic color with mottled variations. In 

 order to find the true color the shells were cleaned with acid and 

 water. When not cleaned the shells are usually of a saffron yel- 

 low or a dirty grey or white color, especially isthesafi"ron yellow 

 discernable on the lower valve. As will be seen in the table, the 

 Alamitos examples have specimens that are of a saffron or orange 

 yellow even when cleaned with acid, that is, when the periostra- 

 cum or outer coating was removed the shells were still shown to 

 be of a saffron color. This was not the case with many other 

 specimens. The interior of the majority of shells was of a rich, 

 reddish brown color up to and around the muscle scar. 



Los Angeles, California, Sept. 30, 1901. 



PLATE IV. 



Fig. I. Pecten {Plagioctenium) aeqiiisulcatits , Cpr. Right 

 valve — lower one. 



Fig. 2. Upper or left valve of the same, showing interior. Ad. 

 adductor muscle impression. (Size of shell, 2 in. high, 2^ long.) 



Fig. 3. Showing organs in situ after the upper mantle has 

 been removed to show the gills: mo, mouth; 1, liver; g, genera- 

 tive organ on the liver; f, foot; ad, ad. mus.; br, branchia or gill; 

 go, gonad or reproductive organs. 



Fig. 4. Upper side of the mantle; under edge containing 

 ocelli, not visible: 1, liver; m. c, mantel cavity; ad, ad. mus.; u. 

 m., upper edge of mantle. 



Fig. 5. Upper mantle removed; gill removed to show the re- 

 productive organs: 1, liver; g, generative organs on the liver; h, 

 heart: r,rectumandanus. a, ad. mus.; mo, mouth; f, foot; k, kidney 

 or nephridium; s, sperm; o, ova; m, mantel border with ocelli. 



Fig. 6. Mouth, lips and palpi. 



Fig. 6. Three views of the foot, upper and lower side and one 

 showing the foot muscle . 



*In order to confirm the opinion of the writer as to the character of the granular layers 

 found on the liver, cross sections were prepared and mounted under the direction of Prof. 

 C. A. Whiting, of I,os Angeles, to whom thanks are due. 



