PTEROPODA. 197 



transversely, and somewhat curving longitudinally. Dorsal side strongly 

 convex transversely, the two inclined faces meeting in a prominent, obtuse 

 angularity along the middle of the length, slightly incurved or concave in 

 a longitudinal direction. The aperture is oblique ; the peristome on the 

 dorsal side receding in a broad sinus, which has a depth of fully half the 

 width of the shell at that point. Operculum unknown. The imperfect 

 specimens give no evidence of the presence of septa. 

 Surface unknown, the shell not having been preserved. The casts present 

 faint evidence of transverse striae, which are also shown in a gutta-percha 

 impression, from a mould of the external surface in figure 20. 



This species, in its full extent, has had a length of more than one hundred 

 millimetres, and the width of the shorter fragment at base is about thirty-five 

 millimetres. The larger fragment, if complete, would have a width of about 

 fifty millimetres. 



Formation and locality. In the Schoharie grit at Schoharie, N. Y. 



Hyolithes aclis. 



PLATE XXXII, FIGS. 82-30 ; AND PLATE XXXII A, FIGS. 23, 24, 25. 

 llynlithe* aclis, Hall. Illustrations of Devonian Fossils: Pteropoda, pi. 27, figs. 5, 6, 7, 10 and 11. 1876. 



Font .in elongate triangular pyramid, gradually and regularly tapering to an 

 acute extremity. Transverse section somewhat semi-elliptical or subtri- 

 angular, a little convex on the ventral side, about twice as wide as 

 high ; the lateral margins obtusely angular, sometimes attenuate from 

 compression. Ventral face gently convex, and slightly curving in a 

 longitudinal direction ; anterior portion extended in a subspatulate expan- 

 sion. Dorsal face highly convex transversely, and obtusely angular along 

 the middle ; very slightly concave longitudinally. Aperture oblique, the 

 margin extended on the ventral side ; on the dorsal side the peristome is 

 not fully determined, but is apparently nearly straight on the sides, with a 

 Binus at the angle. Operculum in general form subelliptical, the body of 



