170 PALAEONTOLOGY OF NEW-YORK, 



218. 1. HOLOPEA SYMMETRICA (n. 573.)- 



Pl. XXXVII. Fig. 1. 



Spire conical, elevated, apex acute ; height much greater than the breadth ; volutions 

 four or live, rounded, ventricose, increasing gradually from the apex ; surface marked 

 with fine, crowded striae, which curve gently backwards from the sutures ; aperture nearly 

 circular. 



This is a very pretty symmetrical shell, with the spire elevated and the volutions 

 ventricose, resembling some species of Paludina. The striae are fine, close, and sometimes 

 crowded together and elevated in fascia or undulations. All the specimens examined present 

 the uniform character here given, and show scarcely a perceptible variation even in the 

 size of the shell. 



Position and locality. In the upper crystalline portions of the limestone at Middleville. 



(State Collection.) 



219. 2. HOLOPEA OBLIQUA ( n. sp.) 



Pl. XXXVII. Figs. 2 a, b, c, d. 



Spiral, oblique, height and breadth nearly equal ; spire very short, acute at the apex, 

 composed of three or four volutions, diminishing rapidly above, the last one very ventricose; 

 a_perture somewhat circular, entire, transversely extended, with the outer lip thin ; surface 

 smooth, or covered with fine striae. 



This shell has heretofore been referred to the Genus Natica, from its general resemblance, 

 though it is not probable that it is a true Natica. It is more oblique, and the spire is shorter 

 and more abruptly acute than in either of the other species described. The aperture, in 

 two specimens examined, is rounded upon the outer side, contracting towards its junction 

 with the body whorl. In the largest specimen seen, the surface is marked witlr vertical 

 curving undulations or rounded ridges ; but these appear due to age, or other circumstances 

 not constant in their inlluence, though something of the kind is obscurely visible in another 

 specimen. The volutions are somewhat more appressed at their junction than the succeeding 

 Species. 



Fig. xJ a. View of the aperture of a small specimen. 



Fig. 2 b. View of the back of the shell. 



Fig. 2 c. Pi ofile view of the same. 



Fig. 2 d. Back of a larger specimen. 



Position and locality. This species occius in the higher shaly part of the Trenton lime- 

 stone at Middleville. Tiie specimen fig. 2 d is from the upper crystalline portion of the 

 rock at VVatertown, Jefferson county. (State Collection.) 



