2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 9I 



Dorsal valve evenly convex, slightly flattened at the front. Sides 

 gently rounded, narrowed at the posterior to form an obtuse beak 

 which curves under the ventral beak. 



Ventral interior : Pedicle collar short ; length of muscle field equal 

 to about one third the length of the valve. Pallial sinuses narrowly 

 divergent. 



Dorsal interior : Loop narrow, equal in length to about one fourth 

 the length of the valve. Crural processes short, transverse ribbon 

 wide, rather sharply folded medianly. 



Discussion. — The shell nearest to Gryphus bartschi externally is 

 Liothyrella uva (Broderip). This species has the lenticular profile of 

 the new species herein described and possesses also the fine radial 

 lines in addition to concentric lines of growth. However, the loop of 

 L. uva is sufficiently different from that of Gryphus to have war- 

 ranted the erection of the dififerent generic name. 



Gryphus bartschi has been misidentified as G. cubensis (Pour- 

 tales), to which it has only a superficial resemblance. The latter is a 

 larger shell with a very different growth habit. (See pi. i, fig. 9.) 

 In profile G. cubensis has a sinuous lateral profile with the greatest 

 curvature at the middle of the valve. The sides of the ventral valve 

 are conspicuously flexed dorsally. Viewed from the dorsal valve (see 

 pi. I, fig. 9), it is triangular in outline, being widest near the front. 

 The anterior commissure is rectimarginate. The triangular outline is 

 also seen in the young of the species. 



In the same general geographic realm as G. cubensis and G. bartschi 

 is another species, G. bartlettii. This is a large species readily dis- 

 tinguished by the strong fold on the dorsal valve. In shape, color, 

 and ornamentation this species differs notably from the one described 

 here as new. 



Type locality. — Station 102, at 90 to 500 fathoms, latitude 

 i8°5o'3o" N., longitude 64°43' W.— latitude i8°5i' N., longitude 

 64°33' W. Occurs in association with Gryphus bartlettii. 



Holotype. — U.S.N.M. no. 431002. 



ARGYROTHECA JOHNSONI, n. sp. 



Plate I, fig. 10; plate 2, figs. 1-12 



Shell larger than usual in the genus, semicircular to subelliptical 

 in outline. Hinge straight, cardinal extremities acutely angular to 

 mucronate in the young, but nearly a right angle in adults and old 

 individuals. Lateral profile plano-convex. Anterior commissure 

 broadly sulcate. Ventral interarea strongly inclined ventrally (pro- 



