1903.] NATURAL SCIENCES OF PHILADELPHIA. 269 



rounded than in that species and become obsolete in the posterior 

 concave area of the whorls. A specimen in the Conrad collection is 

 marked "servata var.?"; it is deprived of the nucleus and adjoining 

 whorls. Both this species and servata occur also in the Lower Vicks- 

 burg, but in slightly modified forms. 



Pleurotoma oblivia n. sp. 



This is a Red Bluff species somewhat allied to servata. It 

 resembles servata in general form and conformation of the nucleus, 

 nepionic whorls, aperture and canal, the elevated smooth nucleus of 

 three or four whorls and nepionic spire whorls being formed in the same 

 way, but the ribs are narrower, more strongly rounded, much more 

 elevated and only about six in number, strongly marked throughout 

 the length of the whorl and only becoming extinct at the rather fine 

 sinuous collar just below the suture. The revolving sculpture consists 

 of eight or nine coarse lyriE, more dilated on the ribs, the first three 

 less coarse and subequal, those in anterior two-thirds of the whorl 

 generally with one fine thread intermediate. Length 22 mm., width 

 6.5 mm. It may be readily distinguished from servata by the fewer, 

 narrower and more elevated ribs, more equal revolving lines through- 

 out the length of the whorls and absence of any defined posterior flat- 

 tened or concave area on the latter. 



Pleurotoma evanesoens n. sp. 



In the Jacksonian of the Kimbrel Beds, outcropping on the Red 

 River a few miles below Montgomery, occurs another P^ewrotoma, rather 

 closely resembling servata in general form, but widely distinct in sculp- 

 ture and even more elongate in form. The nucleus is smooth, rather 

 higher than wide and has about three whorls, the subsequent whorls 

 mutually subsimilar, each having scarcely six large, though feebly 

 elevated, oblique ribs. The collar below the suture is moderately 

 wide but obtuse and low, not sinuous, and, immediately below it, the 

 surface is feebly concave and moderately rapidly expanded to the 

 middle, where each whorl is obtusely tumid and prominent, the sur- 

 face thence gradually declivous anteriorly to the suture. The low 

 feeble oblique ribs become wholly extinct in the concavity, occupying 

 almost posterior half of each whorl. The sculpture is very fine and 

 feeble, consisting of relatively broad but very feebly elevated, flat, 

 revolving lyra, which are very close-set and subequal, mutually 

 separated by a single very fine thread of similar character. The 

 entire sculpture is so feeble that it is very apt to be entirely effaced 

 by water wearing. Length of the largest of the three specimens 



