144 AMERICAN JOURNAL 



above the head. Length of adult specimen -84 in., breadth -64 

 in., altitude -26 in. Defl. of apex 110°, of ant. slope, 54°. 



Length of most elevated specimen -56, breadth -45, alt. -26 

 in. Shell broadest posteriorly, making the outline .somewhat of 

 an egg-oval shape. Number examined, 107 specimens. 



Soft parts. Foot oval, thin. Head broad, rostrum short, 

 above rounded ; below, produced on each side into a tentacular 

 filament, somewhat longer and slenderer than the tentacles. Eyes 

 absent ; tentacles short, thick, with concentric wrinkles setaceous 

 on either side of the rostrum. Mantle edge simple, thickened, 

 slightly striate on the inner side, continuous in front of the head. 

 Over the head extremely thin, varicose. Behind the head on 

 right side are two papillae, being the openings of the generative 

 duct or ovary, and to the left of it, of the anus. Liver and ovary 

 (which fills the apex) of a dark green, completely encircled by 

 the intestine, which is of a dark brown color. Buccal mass large. 

 Jaw thin, translucent, divided by an impressed median line into 

 two portions ; edge entire, simple. 



Rhachidian tooth broadly cordate, bearing three nearly equal 

 black cusps with orange bases. Base thickened ornate, like an 

 ancient lyre with five strings. Inner lateral simple, cusp not 

 much wider than the shaft. Outer lateral posteriorly alate, sim- 

 ple, strong. Base pointed. Shaft wider than the inner lateral, 

 and as wide as the cusp. (See fig. 2, a.) Number examined, 13. 

 Cabi'nets Smiths. Inst., McGill College, Chic. Ac. Sci., Bost. 

 Soc. Nat. History. 



This shell differs from the Lepeta caeca of Europe and Eastern 

 America in its sculpture, so that, even without a knowledge of 

 the animal, the conservative but accurate Middendorf separated 

 it as a permanent variety, under the name eoncentrica. A more 

 thorough knowledge reveals differences in the anatomy which 

 the simplicity of the shells would not lead us to suspect, render- 

 ing a subgeneric separation necessary. Middendorf, ignorant of 

 the genus Lepeta, which had not been characterized, but only 

 indicated by Dr. Gray, proposed the genus Cryptobranchia for 

 its reception, which, restricted as above, is here adopted. This 

 species is the L. ca^coides of Dr. Carpenter. 



Middendorf 's specimens came from the Ochotsk Sea ; Dr. 

 Carpenter's from California and Puget Sound. I have it from 

 St. George's Island, Behring Sea; Ounalashka, Ounga Id., 4 

 fms., Kadiak 6 fms., and 10 fms. shelly mud, Sitka harbor, on 

 stones and dead shells. Also Monterey, which is probably its 

 most southern station. 



Very young specimens of ? Scurria Jiiitra, Esch., might be 



