24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



HELCIONELLA AEQUA, n. sp. 



Plate i, figs. 45-47 



Several examples of a smooth form occur with H. arguta. This 

 species is strongly curved but does not form a complete whirl. It 

 expands very rapidly from the beak to the mouth. Viewed in cross 

 section H. aequo, is so flattened that both sides are nearly parallel. 

 Faint irregular annulations may be seen in proper light. There are 

 also rather weak longitudinal striations toward the Outer margin of 

 the whirl. 



Locality 54s. 



Holotype— U.S.N.M. No. 98487. 



HELCIONELLA BURLINGI, n. sp. 



Plate i, figs. 42-44 



At first it was thought that this form might be H. arguta, which it 

 closely resembles in its coarse annulations, but, as seen in the illus- 

 trations, there is considerable difference in this respect. H. burlingi 

 forms a little more than a complete whirl. In cross section it is 

 rounded with flattened sides, and the annulations are wide but 

 irregular on the outer margin of the whirl, becoming obsolescent on 

 the inner face. The separating depressions are deeper on the sides 

 than on the outer portion of the whirl, contrary to the usual develop- 

 ment. The surface is marked by irregular striations parallel to the 

 annulations, and in addition there are faint lengthwise striations. 



Locality 59L 



Cotypes.-AJ.S.'NM. Nos. 98488a-c. 



HYOLITHIDAE Nicholson 



HYOLITHES Eichwald, 1840 



HYOLITHES PROLIXUS, n. sp. 



Plate 2, figs. 1-3 



This is a large species without a carina. As shown by the photo- 

 graph of the cross section the convex sides rise very steeply from the 

 flat side and the convex side is rounded rather than sharply angular. 

 On the flat side the usual striations are parallel to the lip but are 

 developed irregularly. On the convex side the surface is also 

 striated parallel to the lip except that the striae turn up toward the 

 lateral angles, and they are closer together than on the flat side. 



Locality 54s. 



Cotypcs.— U.S.N.M. Nos. 984893^. 



