LAMP-SHELLS AND THEIR ALLIES 29 



polished epidermis. It has been dredged from deep 

 water off the coast in various places from British 

 Columbia to San Diego. 



The Arcidae^ though very abundant in some parts 

 of the world, are but poorly represented on this 

 coast. In general they prefer warmer waters, being 

 especially common on the coast of Florida. The 

 Arks, as they are called, have a great number of 

 small hinge-teeth which are alike in shape, and taken 

 together they resemble a comb. The shells are gen- 

 erally strong and well developed. 



Area reticulata^ Gmel., the Cross-lined Ark, is 

 very small, and has been found from San Pedro 

 southward. Area mutabilis^ Sby., and Area 7nulti- 

 eostata^ Sby., are occasionally found at San Pedro 

 and vicinity, though really belonging to the fauna 

 of Mexico. 



Glyeymeris intermedia^ Brod., the Medium Ark- 

 shell, is round, like a button, and is about halt an 

 inch across. The shell is solid and white, though 

 tinged with brown, and is marked with many small, 

 transverse hinge-teeth. It was formerly called Axi- 

 nea intermedia. 



Figures 13 and 14 represent the outside and inside 

 of a remarkable shell from northern Alaska. As it 

 was dredged from pretty deep water, it is probable 

 that very few of my readers will ever see a specimen; 

 but it is well to know about some of the rare forms 

 that live in the sea, even if we never have the privil- 

 ege of seeing them. The brown epidermis is densely 

 hairy and the margin of the shell is curiously bent. 



