301 



There seems to be no doubt about the generic affinities of this shell 

 with Cypricardella of Professor Hall. It somewhat closely resembles 

 C. subelliptica, one of the typical species (Iowa Geol. Kept., Vol. i., 

 Part II., pi. 23, fig. 10), but is of a more quadrangular form, and the 

 umbonal ridge is distinctly marked. 



Genus Edmondia, Koninck. 

 Edmondia Burlestgtonensis (n. sp.) 



Shell of medium size, broadly subelliptical in outline, with regularly 

 ventricose valves, breadth equal to three-fifths of the length. Beaks 

 situated within the anterior third, strong, prominent, and incurved. 

 Hinge line and basal margin gently and equally cm-ved ; anterior and 

 posterior extremities broadly and equally rounded. 



Surface marked by numerous strong, concentric undulations, paral- 

 lel to the margin of the shell. In full-grown individuals there is a 

 shallow, undefined sulcus, commencing near the centre of the shell, 

 and reaching the border near the middle of the basal line. 



This species resembles E. ? radiata, Hall (Iowa Geol. Kept., Vol. 

 I., Part II., pi. 29, fig. 3), but difiers in having the posterior extremity 

 slightly narrower than the anterior, instead of much broader ; and 

 also in the concentric undulations. 



GASTEROPODA. 



Genus Euomphalus, Sowerby. 



EUOMPHALUS AMMOISr (n. sp.) 



Shell small, discoid, spire not elevated above the plane of the outer 

 volutions. Volutions three or four, closely coiled, gradually enlarging 

 from the apex, slightly angular on the upper side, rounded below, and 

 on the back. Umbilicus very broad, exposing nearly the whole of 

 the inner volutions. 



Surface of the shell marked by fine, closely-arranged transverse 

 striae of growth, which have a gentle backward curvature from the 

 suture line to the under side of the volution. 



This is a small but very distinct species, the larger specimens 

 measuring about five-eighths of an inch across the disc, and the volu- 

 tion near the aperture having a diameter of three-sixteenths of an inch. 

 In general appearance it resembles E. Spergenensis HaU, of the War- 

 saw hmestone, but difiers in the angularity of the top of the volution, 

 and in the less number, as well as their more rapid expansion ; the 

 spire is never elevated above the level of the outer volutions, as is 

 frequent in that species. 



