PLEUROCERA. 97 



not much elevated ; whorls 7-8, slightly concave, with a distinct, ele- 

 vated ridge, closely overlying the suture and the projectiug shoulder 

 of the succeeding whorl, so as to form a series of steps to the sub- 

 acute apex ; body-whorl large, generally angulated or distinctly ribbed 

 at base, which is not much rounded ; sutures impressed ; aperture sub- 

 rhoraboidal, whitish within ; outer lip much bent forward towards the 

 base ; columella straight, produced into a narrow deep sinus, which is 

 slightly recurved. 



Length, -85 inch (22 millim.) ; diameter, -42 inch (11 millim.). Length 

 of aperture, '30 inch (8 millim.) ; breadth of aperture, '20 inch (5 

 millim.). 



Habitat. — Alabama. 



Observations. — Belongs to the group of which iLT. canaliculata may 

 be considered the type. It is, however, much less elevated than 

 M. canaliculata, has not the conspicuous grooving on 

 the body-whorl as in that species, and its spire has the ^'S- ^®*" 

 whorls flat instead of exhibiting an obtuse carina, as 

 described by Mr. Say ; a sharp elevated carina at the 

 base of the whorls closely overlies the suture beneath ; 

 the extreme upper whorls having this more distant from 

 the suture become distinctly carinated. The regular 

 gradation of the whorls is its most distinctive character. 

 — Anthony. 



Very closely allied to T. arata, Lea. The figure is from 

 Mr. Anthony's original t3-pe. The shell described as exhnia 

 by Mr. Anthony is the j'oiing of gi-adahim, and the latter 

 name is retained as being more characteristic of the species. 

 For a complete suite of young and old specimens, I am 

 indebted to Prof. Haldcman, who collected them in IIol- 

 ston River, "Washington Co., S. AY. Virginia. I suspect that 

 Mr. Anthony's locality, "Alabama," for gradatum, is incorrect. 



Mr. Lea has recently described the same species as Trypaii- 

 ostoma curtcdum, his shells being rather shorter and more obese 

 than Mr. Anthony's type of gradatum. Some of tlie varieties 

 of this species are finely banded, and others sharply carinate. 

 The following is the description of 



31elania eximia. — Shell deeply sulcate and carinate, ovate; of 

 a beautiful, light, apple-green color, ornamented with two dark-green 

 bands, and an elevated, prominent carina of a light color revolving 

 L. y. w. s. IV. 7 



