174 PALJEONTOLOGY OF NEW-TORK. 



This species, in form, bears considerable resemblance to the one cited above ; but it is 

 uniformly smaller, more distinctly striated, and has the spire more elevated, witli the 

 volutions vertically elevated at the suttires. The umbilicus is also smaller than in E. qual- 

 teriatus, and the outer margin less nearly vertical. It is distinguished from the preceding 

 species, with which it has usually been confounded, by the greater elevation of the spire 

 and the convexity of the volutions, and also in the form of the aperture, which is nearly 

 subquadrate. It is a very neat symmetrical species, occurring much more rarely than the 

 P. lenticularis. 



Fig. 7 a. View of the aperture and front of the shell, showing- the elevation of the spire. 



Fig. 7 b. View of the top of the spire. 



Fig. 7 c. View of the base, showing the umbihcus. 



Position and locality. In the lower part of the Trenton limestone at Middleville. 



225. 13. PLEUROTOMARIA SUBCONICA ( n. sp.). 



Pi.. XXXVII. Figs. S a, b, e, d, e. 



Compare Trothia eUiptieui, Hisinger, Leth. Suecica, pag. 35, pi. 11, fig. 1. 



— trochiformu, Por7i.ock, Geol. Rep. Londonderry, 1843, pag. 414, pi. 30, fig. 9. 



Trochiform ; spire elevated, apex acute ; volutions about five, flattened above, with a 

 projecting carina just above the suture ; last volution strongly carinated on the outer edge, 

 and marked with a spiral band, ventricose below ; aperture transverse, subquadrate, an- 

 gular on the outer side and round below ; surface marked by fine striae, which bend gently 

 backwards from the suture, and more abruptly on the lower part of the whorl ; spiral band 

 a distinct groove, margined by sharp elevated edges, upon which the striae bend backwards 

 in an abrupt curve ; below this the striae bend gently forward, and thence curving back- 

 wards, terminate in the umbilicus ; longitudinal striae crossed by transverse sharp elevated 

 lines which are finer than the longitudinal ones. 



This is a beautiful trochiform shell, with a symmetrical conical spire, and beautifully 

 cancellated surface. The finer concentric striae are often obliterated from wearing or ma- 

 ceration, the longitudinal ones only remaining, and these also are often obliterated. The 

 spiral band is distinct on the last volution, and the striae upon it appear to be crowded into 

 ridges. The suture is formed just at the lower margin of the band, leaving it visible at the 

 lower edge of the higher volutions. In casts of this species, the outer angle of the last 

 volution is distinctly carinated, as also the lower margin of the higher volutions. 



Fig. 8 a. Front view of a specimen preserving the shell in a very perfect manner ; the aperture im- 

 perfect. 



Fig. 8 b. Base of the same, showing the small partially closed umbilicus. 



Fig. 8 e. An enlarged portion of the surface, showing the cancellated striae which arc scarcely visible 

 to the naked eye 



Fig. 8 d. Cast of another specimen. 



Fig 8 e. Front view of the same, showing the form of the aperture. 



