The Duck-bill Shells and Lantern Shells 



The "Wavy Thracia (T. undulata, Conr.) is a rare species, 

 larger and thinner than T. curia. The wrinkles are wavy on the 

 posteria area. The general form of the valves is circular, with 

 central umbones. It is found on the west coast. 



THE SEA BOTTLE SHELLS 

 Genus MYTILIMERIA, Conr. 



Shell bivalve, rounded-oval, thin, fragile, usually inflated, 

 with terminal spiral beaks, somewhat distant. Hinge without 

 teeth; epidermis thin. Species few. 



Nuttall's Mytilimeria, or Sea Bottle Shell (M. Nuttalli, 

 Conr.), thin and fragile, is the type. The peculiarity of the whole 

 genus is that the mollusks live together and make a common nest. 

 This species nests among the colonies of sea-bottles, or compound 

 ascidians. The delicate, white, bladder-like shell is protected by 

 a brown epidermis, and by the ascidians which conceal it. Length, 

 I inch. 



Habitat. — California. 



The Rock-dwelling Mytilimeria (M. saxicola, Baird) has 

 a protean form, as it grows to fit the hole it enters. Pear-shaped 

 when not crowded too much, the shell has a narrow and short 

 anterior end ; it is broadened, swollen and abruptly truncated at 

 the posterior end. The brown epidermis is rough. The hinge 

 plate, large, thick and concave, replaces an ossicle. 



This is the mollusk, without a doubt, that Baird called Lyon- 

 sia, and Keep calls by the sub-generic name Entodesma, Phil., 

 the Rock Entodesma, E. saxicola, Baird. Length, 4 to 5 inches. 



Habitat. — Puget Sound. 



Genus PANDORA, Hwass 



Shell unsymmetrical, right valve flat, left one convex, close 

 shut, attenuated behind; two diverging grooves from apex of left 

 valve. A small genus widely scattered, chiefly in cold waters. 

 About twenty-five species. 



The Three-lined Pandora (P. trilineata, Say) is a delicate 

 little bivalve, in its pellucid white shell, too thin, almost, to cast 

 a shadow. The lining of the shell is iridescent. Its hinge line 



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