Casey — Notes on the Pleurotomidae. 141 



similar to that characterizing Scobinella, and the aperture, 

 canal and embryo are of corresponding form, but the anal 

 sinus is wholly different in form and position and the outer 

 lip is not advanced and arcuately lobed. They have occurred 

 thus far only in the Lower Claiborne Eocene of Texas, and 

 those before me may be readily recognized as follows : — 



Broadly rhomboidal in outline, the spire evenly conical, the aperture and 

 very short canal combined constituting nearly half the entire length; 

 lyrae of the body whorl below the periphery very coarse and widely 

 spaced, alternating with single fine raised lines; colurnellar folds two 

 or three in number. Length of a specimen of 5 body whorls, 11.5 mm. ; 

 width, 4 mm crassiplicata Gabb 



Narrower, the spire subveutricose or narrowing more rapidly toward the 

 apex ; aperture very much less than half the entire length 2 



2 — Larger species, with a nodulose subsutural spiral and a similar but 

 broader duplex peripheral spiral, the two separated by a concave sur- 

 face which is rattier longer than the subsutural collar, and having a 

 fine nodulose thread at its middle; another similar fine thread is very 

 close to the lower margin of the large peripheral spiral, and, below 

 this on the body whorl, the lyrae are equal, granose and moderately 

 widely spaced, the lines of growth fine, deep and close-set, appearing 

 between the lyrae but independent of the nodules; colurnellar folds 

 about three in number. Length of a specimen of 5 body whorls, 9 mm. ; 

 width, 2.8 ram conradiana Aid. 



Smaller species, with numerous very close-set spirals of coarse nodules, 

 the subsutural gradually splitting into two finer spirals on the larger 

 whorls, the concave space below the collar short and with fine irregu- 

 lar thread or threads; spirals below the peripheral alternating in size 

 to the aperture, then equal and almost in mutual contact to the base of 

 the shell; nodules in longitudinal lines" from one lyra to the next, 

 giving a closely costulate appearance which does not exist in the pre- 

 ceding species; columella with two large rounded and very approximate 

 folds at the middle, the lower more oblique than the upper; embryo of 

 about four whorls, higher than wide; aperture and canal relatively 

 longer than in conradiana. Length of a specimen of 3 body whorls, 

 3.9 mm. ; width, 1 .75 mm parvula n. sp. 



These species are all well represented in the cabinet of Mr. 

 Aldrich, to whom lam indebted for the material at hand. 



Trypanotonia Coss. 



A very distinct genus, apparently confined to the middle 

 Eocene faunas of the southern United States and character- 

 ized by the comparatively small size and slender form of the 



