l(j BIOLOGICAL SOCIETY OF WASHINGTON. 



Indirectly, through the influence of protective mimicry, the 

 coloration of shells which frequent beds of seaweed or rocks 

 covered with stony algae, is often modined in harmony with 

 the environment even when the species is not phytophagous. 



In the deeps these influences are wanting and the develop- 

 ment of color is necessarily the result either of uueradicated 

 hereditary tendency, or of some physical features of the en- 

 vironment which operate mechanically and are not yet under- 

 stood. 



The colors chiefly effected by deep sea mollusks are pink or 

 reddish straw color, salmon color, and various shades of brown. 

 These are found in the shell and are more or less permanent. 

 The epidermis of deep sea shells is usually pale yellowish, but 

 frequently is of a delicate apple green, such as is seen in many 

 fresh water species ; and sometimes of a beautiful rich dark 

 chestnut brown, a color also not rare among land and fresh 

 water species. The most common pattern when any exists is 

 that formed by squarish dark spots which occasionally become 

 fused into bands. Among the Archibenthal species found in 

 depths from 100 to 300 fathoms this pattern of brown squarish 

 spots arranged in spiral series is notable in such forms as 

 Scapluila funonia, Aurinia dubia, Halia priamus, Conus mazei, 

 etc. Instances of the green epidermis are afforded by the vari- 

 ous species of Niccididce, Turcicula and Buccinid^. 



The thick and solid layers of aragonite, of which many 

 shallow water species are chiefly built up, are represented in 

 deep water forms by much thinner layers, while the nacreous 

 layers are, if not more solid in abyssal shells, -at least more 

 brilliant and conspicuous, perhaps because less masked by 

 aragonitic deposits. A very large proportion of the deep water 

 shells are pearly and derive their beauty from the brilliance of 

 their nacre. 



