1888.] NATURAL SCIENCES OF PHILADELPHIA. 135 



Dorsal valve with umbo but slightly projecting beyond the hinge 

 line, outer profile having an S like or line of beauty curve, with the 

 concavity at the apical end and the convexity anteriorly; inner 

 or marginal profile regularly convex. Area small. Ventral valve 

 strongly convex in profile, inner profile concave ; area triangular, as 

 high as wide, with the foramen occupying one-half of its width. 

 Surface marked by strong radiating striations which seem to increase 

 mostly by interstriation : they are from ten to twelve to fifteen in num- 

 ber on each lobe at the margin. These are crossed by lines of growtk 

 which vary in distance from each other and increase in definition as 

 they approach the margin. 



This little shell belongs to the same group of orthidean forms as 

 Orthls hiloha Lin. PI. VII, fig. 6. and 0. varica Con., and when 

 first fomid was regarded as an example of the former, but upon com- 

 2)arison with some Wolcott, N. Y. specimens it was found to differ much 

 more from that and 0. varica than they do from each other. The 

 principal points of specific distinction are the more elongate outline 

 of the shell with longer and more pronounced lobes ; a deeper anterior 

 sinus, more acute rostrum and a greater disparity between the size 

 and curvature of the two valves ; and a hinge line which is compara- 

 tively only about one-half as long as that of the species under com- 

 parison. Only two perfect si^ecimens have been found, but occasion- 

 ally a single valve is seen imbedded in the shales of the middle and 

 lower thirds at Lockport. 



Not a single individual of 0. hiloha has fallen under my observa- 

 tion from this vicinity. 



Hyolites subimbricatus, (n. sp.) PI. VII, fig. 7. 



Shell conical, sides regularly sloping from acute apex, aperture 

 about half as wide as height of shell. Surface marked by very faint 

 and closely arranged minute longitudinal strise, which are crossed 

 by irregular transverse strife placed at various distances apart, with 

 occasional stronger lines of growth which at times take on a sliglitly 

 imbricating character. 



On account of the partly flattened condition of the only exami^le 

 thus far secured, the exact angle of divergence of the sides from each 

 other, and the outline of the aperture cannot be ascertained. 



This species bears some x'esemblance to H. columnuris of Barrande, 

 as figured by him, but the longitudinal stri^ are very much finer and 

 more closely arranged, so that they are hardly noticeable except 

 under a lens, and the shell is not so tapering. 



