Morse.] 



144 [April 5, 



Lacuna neritoidea, Mr. Fuller has observed spawning on bladder 

 weed and its yellowish tinge accords well with its surroundings. 

 Margarita helicina I have found in numbers on the large Laminarian 

 and on sea weed at low water mark, and its color is decidedly protec- 

 tive; while other species of Margarita dredged in deep water on 

 shelly ground are whitish, pearly, or red. 



The protective coloring of certain species is well seen upon stones 

 dredged in deep water, the various mollusks adhering to them, closely 

 resembling the calcareous algas and the stones themselves. 



Species peculiar to sand beaches are of various sand colored shades, 

 as for example Machara, Mactra, CocJrfodesma, Cyprina, the little 

 Solenomya and Solen. On muddy ground we notice certain Tellinas 

 and other species with white shells. It has been supposed that those 

 species hidden from the light were generally white, and this would 

 seem to be the case when we recall Mya, certain species of Teredo, 

 Tellina, Pholas, and other species. Yet we do have cases where the 

 shell is oftentimes conspicuously banded or marked. It might appear 

 that in those species living buried in the mud or sand, the shell was 

 protected by a very thin epidermal layer, and that this layer was 

 eroded, thus exposing the white shell ; there are certain species, how- 

 ever, living buried in the mud or sand which have an epidermal coat 

 very thick and dark brown or black, such examples are seen in So- 

 lenomya borealis and Glycymeris siliqua. 



It has been noticed that the same species occupying different sta- 

 tions are differently colored. Dr. A. A. Gould noticed this in regard 

 to A.starte castanea ; those thrown up from deeper water are darker 

 colored than those found in quiet sandy places. In his report on 

 the Invertebrate Animals of Massachusetts, first edition, p. 78, speak- 

 ing of the shells found in the sandy harbor of Provincetown, he says : 

 "The color of all the shells in that harbor is remarkably light." 



A very evident case of protective coloring is seen in the three spe- 

 cies of Crepidula found on our coast. Crepidula fornicata is drab, 

 variously rayed and mottled with brown, and it lives attached to 

 stones near the roots of the large Laminarian or upon stones clothed 

 with algse of similar colors, or attached to the large Mydlus. Cre- 

 pidula convexa, a much smaller species, lives on the roots of sea weed. 

 Prof. Perkins records its occurrence on the black shell of Ilyanassa 

 obsoleta. This Crepidula has a very dark brown shell, according well 

 with the dark color of its various places of lodgement. Crepidula 

 plana or unguiformis lives within the apertures of the shells of larger 



