Casey — Notes on the Pleurotomidae, 149 



to be paucispiral, but the drawing shows a multispiral proto- 

 conch ; this is, however, a matter of minor importance. The 

 anal sinus is broad, sometimes very feeble and always median 

 in position on the spire whorls though not identified with 

 any particular one or more of the subequal and rather coarse 

 flat spirals . The beak has no external oblique tumidity . There 

 can be but little doubt, in view of geographical variations and 

 wide distribution of this genus, ihsit Undiatoma, of Cossmann, 

 should be regarded as a synonym or as constituting a slightly 

 differentiated section of Asthenotoma. The American species 

 known to me may be recognized as follows, the characters of 

 texana and shdleri being taken from accurate drawings and 

 descriptions. They are all peculiar to the Lower Claiborne 

 Eocene : — 



Concavity below the subsutural carina large, extending very nearly to the 

 middle of the whorl, the surface thence to the lower margin having 

 three to four equal and widely spaced spiral lines; spire almost twice as 

 long as the aperture and canal combined. Length of a specimen of 9 

 body whorls, 18 mm. Texas texana Gabb 



Concavity below the subsutural carina very short 2 



2 — The concavity much longer than the intervals separating the four or five 



spiral lyrae below it; spire rather rapidly acuminate, apparently not 

 more than one-half longer than the aperture and canal together; form 

 unusually stout; columella straight. Type defective but probably 

 representing a specimen of about 8 body whorls, having a length of 



14 mm. Louisiana shaleri Vgn. 



The concavity not longer than the intervals separating the large lyrae below 

 the middle of the whorls 3 



3 — Form somewhat as ia the preceding species, the spire rapidly tapering 



and not more than one-half longer than the aperture and canal com- 

 bined, the inner outline of the columella broadly, evenly arcuate; 

 spire whorls with a strong flattened subsutural lyra, bordered beneath 

 by a feeble concavity not longer than a seventh or eighth of the total 

 length of the whorl, succeeded by two smaller and more approximate 

 carinules and these by four strong lyrae occupying the entire space 

 thence to the lower margin; on the larger whorls there is a single 

 small raised line alternating with the last-named lyrae. The obtuse 

 ribs of the nepionic whorls are few in number and become completely 

 obsolete on the fourth or fifth whorl. Length of a specimen of 7 body 

 whorls, 12 mm.; width, 3.4 mm. Texas (6 miles south of Wheelock) — 



Mr. T. H. Aldrich eximia n. sp. 



Form very much elongated, the spire apparently more than twice as long as 

 the aperture and canal combined, gradually, evenly acuminate ; colum - 

 ella somewhat obliquely tumid; spire whorls each with a very coarse 



