Casey — Notes on the Pleurotoniidae. 145 



remainder of the shell in r/«66i, which is assumed as the type. 

 The species before me may be distinguished by the following 

 characters : — 



Columella straight and unmodified; embryo very large 2 



Columella with a stout plica at about the middle of the aperture proper; 

 embryo much smaller, though of the same general type 3 



2 — Embryo stout; subsutural collar flat, composed of two, and, subse- 



quently, about three, coarser spiral carinules; concavity below the 

 subsutural collar, long, concave; periphery anterior in position, 

 rounded In profile, moderately swollen, with the spiral lines larger. 



Lower Claiborne of Wheelock, Texas gabbi Con. 



Embryo large but much narrower, the lower whorls similarly, though more 

 coarsely, costulate, the upper smooth whorls forming a much more 

 I acutely elevated apex; subsutural surface broadly, feebly swollen and 

 covered with numerous fine but strong carinules merging gradually 

 into the small threads of the subjacent concavity; remaining charac- 

 ters nearly as in gabbi, the beak more rapidly tapering, very slender at 

 tip, the aperture and canal together but little longer than the remain- 

 der of the shell. Length of a specimen of 5 body whorls, 23.5 mm.; 

 width, 6.8 mm. Lower Claiborne Eocene of Smithville, Texas — 

 Mr. Aldrich tenuirostris n, sp. 



3 — Form nearly as in the two preceding, the embryo very much smaller in 



size, conical, with the lower whorls ribbed; subsequent whorls each 

 with a strongly and abruptly elevated double carina at basal third, the 

 two carinae becoming more widely separated and with an intermediate 

 thread on the larger whorls; space between the double carina and the 

 subsutural cariniform collar broadly concave and with strong and widely 

 spaced spiral threads; double carina of the first two body whorls 

 crenulate. Lower Claiborne Eocene of Wheelock, Texas — [BorsO' 

 nia] plenta H. & A. 



The last of these species may possibly be subgenerically 

 different from the others but certainly cannot be further 

 removed. The species figured by Harris as the young of 

 plenta is probably specifically different. 



Eosurciila n. orcn. 



a 



The embryo in Eosurcula is much narrower than in Pro- 

 tosiircula, strongly elevated and smooth throughout, the sub- 

 sutural collar smaller and less developed, the fasciolar surface 

 thence obliquely ascending but straight in profile or nearly so 

 to the obtusely angulate periphery, on and below which the 

 spirals become coarser. The aperture and canal are nearly as 



