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AMERICAN JOURNAL 



stouter and thicker. Epidermis of a deep yellow brown, instead 

 of waxen ; shape more trigonal with the posterior ventral mar- 

 gin more produced ; umbones dark umber brown ; ligament 

 longer, stouter and much more prominent ; lunule almost obso- 

 lete, with the waves continued over it instead of smooth. Con- 

 centric sculpture in waves, not separated by grooves as in L. 

 Jluetuosa of the same size, but further apart, more irregular and 

 rounded or sharp instead of flattened. Hinge line broader, teeth 

 larger and much stouter than in any other species ; pallia! sinus 

 shallower and rounder, and muscular impressions proportionate- 

 ly larger than in any other form of the genus. Animal dark 

 brown. Lon. -8. Alt. -64. Diam. -36 in. 



Habitat. Fort Simpson, British Columbia ; Capt. C. M. 

 Scammon, U. S. Revenue Service. Six specimens. 



This species, differing from any in the collection of the Brit- 

 ish Museum, with which it was compared by Dr. Dawson, is 

 readily recognized by its stout teeth, thick shell, dark color and 

 large ligament. The umbones are more central and the pallial 

 sinus shallower than in any of the others. 



LlOCYMA VIRIDIS. n. S. 



Habitat. Arctic Ocean, Capt. Rodgers, U. S. N. 



Shell of a beautiful pea-green, covered with a beautifully 

 polished epidermis ; sculpture of very fine rather sharp concen- 

 tric waves, very regular in outline. Epidermis between the 

 waves raised in minute bubble-like globules. Numerous faint, 

 rather distant impressed lines, not stride or grooves, radiating 

 from the umbones, which are rather small and acute. Shell 

 thin but not compressed, waves not flattened. Hinge line very 

 narrow, teeth slender but distinct, very close together. Um- 

 bones in the anterior third. Ventral margin produced and 

 greatly arched. Anterior end rather pointed, short. Pallial 

 sinus small, sharply angulated. Muscular scars small. Hinge 

 line very slightly arched. Lon. 1-0. Alt. -66. Diam. -3(3 in. 

 Lunule smooth, lanceolate, bounded by an impressed line. Liga- 

 ment short, small, not prominent. 



This exquisite shell was rather hastily referred to by me in 

 my description of L. fluctuosa as a variety of it. Finding that 

 there is very little variation in the different species of this group, 

 of some of which I have examined several hundred specimens, 1 

 have come to the conclusion that it is distinct. 



I have been unable to find any approach to it among the other 

 species, of which I had but a small series at my first writing. 

 The animal is of a fine pea-green color. The shell is readily 



