191*).] NATURAL SCIENCES OF PHILADELPHIA. 167 



This flattened form is assigned to the familj Euomphalidae because 

 of its flat spire, its dee)) wide umbilicus, the outer margin of which 

 is produced conspicuously and further on account of the angular 

 peripheral margin. Hippocampoidcs resembles Discolx lix somewhal . 

 but differs from it in having a protoconch not inverted and further 

 in not having a whorl with a quadrate cross-section. It may be 

 separated from Straparollus by the height of the spire and cross- 

 section <>f body whorl. 

 Hippocampoides serratus ~i> nov. PI. XXIV. figs. 11, i_\ 13. 



Description. — Shell rather small, flattened or very feebly convex, 

 apically concave laterally, the altitude increasing toward the aperture, 

 profoundly umbilicate; protoconch minute, planarboid depressed 

 below the plane of the initial whorl of the conch, the one and one- 

 half component volutions rather loosely coiled and approximately 

 uniform in diameter, line of demarkation between conch and proco- 

 conch indicated by a slight but very abrupt increase in the diameter 

 of the whorl; conch thrice coiled, the whorls increasing regularly and 

 quite rapidly in diameter; external surface smooth and probably 

 polished in the original state; peripheral keel acute, sharply and, on 

 the final half turn, profusely serrate; the indentation nearest the 

 aperture running almost half way to the suture line; the deepest of 

 the serrations coincident with pronounced resting stages so the 

 last half turn seems to be made up of a series of overlapping tri- 

 angular plates; suture line rather deeply impressed; aperture semi- 

 elliptical in outline, the aperture half again as great as that of the 

 body whorl at its initiation, but less than half that of the body whorl 

 at its close; peristome adnate along the body wall, very feebly emargi- 

 nate both at the peripheral and at the umbilical keels, approximately 

 straight between the notches, umbilicus very wide, profound, 

 persistent to the apex, funicular, the outer margin acute, probably 

 serrated; area between the peripheral and umbilical keels quite 

 symmetrically concave. 



Dimensions. — Altitude. 11 mm.; length of aperture. 5 mm.: 

 maximum diameter. 19.2 mm. 



This species is remarkable for the auriculate outline of the apical 

 aspect, the deep serrations of the periphery, the rapid increase of the 

 altitude of the shell toward the aperture, the lateral concavity and 

 the profound umbilicus, approximately half as wide as the entire 

 shell and margined by an acutely angulated keel. The edge of the 

 keel has been macerated, but there is evidence that it was quite 

 strongly serrate. 



