PLATE 60. 
Fig. 1. 649. 2. Platyostoma niagarensis. ( Pag. 287.) 
la, 6, c. Toung individuals, where the spire is depressed as low as the outer volution. 
1 d. An individual having the spire equally depressed, and the surface conspicuously marked by longitudinal 
strise. 
1 f. A small specimen having an elevated spire, with the surface marked as in fig. 1 d. 
1 g. View looking on the spire of a similar specimen. 
1 h. A small specimen having the spire much elevated, and the volutions longitudinally and transversely 
striated. 
1 i, k, l. Back, summit and front views of a globose specimen preserving its natural proportions. 
1 m, n. Two views of a similar specimen, having the aperture somewhat more expanded. 
1 o, p. Two views of a larger individual with an expanded aperture and a strong fold upon the back of the 
volution, and a sinus in the margin of the aperture. 
1 r. A similar larger specimen. 
1 s, /, Yiew of spire, and partial front view of a large specimen from which the shell is partially exfoliated. 
1 u, v. Yiew of the summit of two other individuals having the usual depressed spire of this species. 
Fig. 2. 650. 3. Platyostoma hemispherica. ( Pag. 288.) 
2 a. Yiew of the summit. 
2 b. Front view. The shell is so much depressed, that the figures can give no true idea of the aperture. 
Fig. 3. 
651. 1. Acroculia niagarensis. 
652. 
2. Acroculia angulata. 
(Pag. 288.) 
(Pag. 289.) 
4 a. The back of a small specimen, where the shell is scarcely preserved. 
4 b. Upper side of the same. 
4 c. Back of another specimen, where the angles, carina, and surface striae are well preserved. 
4 d. Upper side of the same, showing in part the expanded aperture and the minute volutions of the at¬ 
tenuated apex. 
