TRENTON LIMESTONE. 171 



220. 3. HOLOPEA PALUDINIFORMIS. 



Pl. XXXVII. Figs. 3a,b. 

 Plewrotomaria. Emmons, Geol. Report, 1842, pag. 397, fig. 1. 



Spiral, scarcely oblique, elevated ; height greater than the breadth ; volutions four or 

 more, rounded, ventricose, enlarging somewhat rapidly from the apex ; aperture round 

 ovate ; Burface 1 The specimen is a cast, preserving no surface markings. 



This species resembles the first described, but it is comparatively more gibbous, and the 

 spire less elevated in proportion to the size of the shell. In form and aperture, it closely 

 resembles the larger Paludinje. 



Fig. 3 a. View of the back of the shell, h. View of the aperture. 



Position and locality. The only specimen known, is from the crystalline upper part of the 

 Trenton limestone at Watertown, Jefferson county. (^state CoiUction.) 



221. 4. HOLOPEA VENTRICOS A ( n. *p.). 



Pi.. XXXVII. Figs. 4 a,*. 



Spiral, oblique, subglobose, very ventricose ; height and breadth nearly equal ; spire 

 short ; volutions about three, rounded, rapidly enlarging from the apex, and becoming 

 ventricose ; aperture rounded oval, slightly contracting at the upper side ; surface ? 



The specimen is a cast, preserving some slight evidences of striae as in fig. 1, which 

 appears to have been the prevailing character of the markings on the surface. But few 

 specimens of either of the species have been seen, and they are much more rare than the 

 PLEtjROTOMARiA, and occur almost entirely or altogether in the upper part of the rock. 



Fig. 4 a. View of the back of the spire, b. View of the top of the spire. 



Position and locality. In the upper crystalline part of the Trenton limestotie at Middle- 

 ville, Herkimer county. 



Several other imperfect specimens, apparently referable to this genus, have been observed 

 in the Trenton limestone, but none of them in a condition to furnish specific characters. 

 There are smooth casts of PleurotoMaria, resembling in general form these or smaller 

 species of the same genus, being sometimes regularly rounded ; but in most instances they 

 preserve some evidence of the angular form of the last volution, which is never seen in the 



HoLOPEA. 



22* 



