98 PALJ;ONTOLOGY OF NEW-YORK. 



136. 10. LINGULA OBTUSA { n. sp.). 



Pl. XXX. Figs. 7 a, b, c. 



Broad-ovate, obtuse at the apex and regularly rounded below, depressed in front, but 

 very prominently convex on the umbones ; beaks obtuse, prominent, not terminal ; margin 

 of the shell a little produced beyond the beaks ; surface apparently smooth, but, under a 

 magnifier, exhibiting fine concentric and radiating striae. 



This shell is easily distinguished by its ovate form, with very obtuse apex ; the beak is 

 prominent and elevated, with a narrow space between it and tlie margin of the shell. The 

 outline from beak to base is much more arched than in any other species. 



Fig. 7 ffl. A very perfect specimen of large size, giving the exact form of the shell : radiating striae 



scarcely visible. 

 Fig. 7 b. Another specimen, the form not quite as perfect as in the last, but the radiating strise more 



distinctly visible. 

 Fig. 7 #. A smaller individual of the same species. 



Position and locality. In the more shelly central part of the Trenton limestone at Middle- 

 ville, Herkimer county. (S'a'f Collection.) 



137. 11. LINGULA CRASSA (71. s/*.). 



Pl. XXX. Figs. 8 a, b, c, d, e. 



Broadly ovate, with a subacute beak ; one valve more convex than the other, and some- 

 what arched ; shell thick, marked by strong concentric elevated lines, without radiating 

 striae. 



This shell is broad and regularly rounded in front, sloping abruptly to the beak. The 

 thick shell and prominent concentric lines arc characteristic. The shell is black, and less 

 brilliant than the Lingul.5; usually are. I have seen but one perfect specimen. Single 

 valves and fragments are abundant in the limestone at Basin Harbor (Vermont). It. is 

 also apparently the same species, in fragments and smaller individuals, which sometimes 

 abound in the silico-argillaceous limestone intercalated among the slates east of the Hudson 

 river near Troy, showing its geological range to be from the Trenton limestone through 

 the Hudson-river group. 



Fig. 8 a, b. View of both valves of this species. 



Fig. 8 «. View of the edge of both valves, closed ; one being more convex than the other, and slightly 



arched. 

 Fig. 8 d. A larger specimen, apparently of the same species, somewhat crushed. 

 Fig. 8 «. A smaller specimen, apparently of the same species. 



Positionand locality. This species occurs at Middleville, in the central part of the Trenton 

 limestone ; also in the same rock at Basin Harbor and Crown Point on Lake Cliamplain. 

 A species, similar or identical, in limestone among the shales of the Hudson-river group, 

 near Troy. 



