254 



PALiEONTOLOGY 07 NEW-YORK. 



Fig. 4 n. A cast of the ventral valve of this species, showing the hilobate character of the mus- 

 cular impression, the cavities of the teeth, etc. 



Fig. 4 o. An enlargement of the surface, showing the longitudinal diverging and fine concentric 

 striae. 



Positioii and locality. This species occurs at all the localities of the shale from Wolcott to 

 the Niagara river, but the best specimens have been found in the vicinity of the former place. 



615. 28. ORTfflS PUNCTO-STRIATA («. sp.). 



Pl. LII. Fig. 5 o -/. 



Sub-globose ; valves nearly equal, extremely convex or inflateil in the middle ; beaks ex- 

 tended, that of the dorsal valve somewhat longer and incurved ; hinge-line shorter than the 

 width of the shell ; area shorter than the hinge-line, comparatively rather broad, and occupying 

 both valves ; surface marked by fine equal stria, which bifurcate at intervals on the upper part 

 of the shell ; depressions between the striae, particularly in slightly worn specimens, punctate. 



This species is readily distinguished from the preceding, or any other species of this period, 

 by the extremely convex valves and strong prominent beaks, with a proportionally short hinge- 

 line. The striae are flattened, and the bifurcations take place mostly above the centre of the 

 shell. The concentric striae are extremely fine, and rarely preserved in the specimens examined. 

 The puncta between the striae give the surface a very peculiar and characteristic aspect. 



Fig. 5 a. View of the ventral valve of a small specimen, showing the beak of the dorsal valve, 



and a part of the area above it. 

 Fig. 5 6. A profile view of the same specimen. 



Fig. 5 c. A cardinal view of a larger specimen, showing the great convexity of the valves. 

 Fig. 5 d. A large dorsal valve which has been flattened by pressure. 

 Fig. 5 e. The interior of the same. The form of the muscular impression can not be ascertained, 



the shell being filled with calcareous matter. 

 Fig. 5 /. Several of the striae enlarged, showing the puncta between. 



Position and locality. This species was found in the lower part of the limestone at Lock- 

 port. (Collection of Col. jEwnxT.) 



616. 29. ORTHIS FLABELLULUM, Var.'? 



Pl. Lll. Fig. 6o-g. 



Orthii flabellulum (a)? Rep. 4th Geol. Dist. N. York, 1843, pag. 105, fig. 5, and p. 107. 

 Compare Orthis flabellulum (a), Sowerbv in Mukchison's Silurian System, pag. 639, pl. 21, 

 fig. 8. 



Shell semioval ; hinge-line equal to the width of the shell ; surface marked by twenty-four 

 to thirty simple rounded plications, which are equal to the space between them ; plications 

 usually smooth, with the remains of concentric striae crossing the depressions between, and 



