FOSSILS OF THE HUDSON EIYER GROUP. 83 



bonal ridge and narrow cardinal slope ; anterior end rounded and passing 

 into the broadly rounded basal line ; posterior end oblique, pointed be- 

 low; hinge line short; beak very small. Hinge plate occupied by six 

 angular, crenulated, radiating teeth, which diverge from beneath the 

 beak, and are strongly arched upwards between their origin and extrem- 

 ities ; crenulations minute, but very distinct; muscular impressions and 

 pallial line not observed." 



The specimens of this species that have been observed lay imbedded 

 on the surface of limestone blocks, and present the inner side of the shell 

 to view, so that the exterior features of the shell have not been seen, 

 consequently a full description of the species can not be given. The 

 species dift'ers in the general form from L.postriata, and also from L. plana, 

 found in the same geological position in New York, in the more equal 

 length and breadth of the valves. The form is somewhat similar to that 

 of Tellinomya levata, associated w^ith it, but the angularity of the umbonal 

 ridge will serve to distinguish it externally, while the concavity of 

 the posterior hinge line, as well as the form of the teeth, will readily 

 distinguish it internally. 



Formation and locality : In the limestones of the Hudson River group, near Cincin- 

 nati, Ohio. The originals were from the collection of C. B. Dyer. 



Genus MODIOLOPSIS, Hall. 



(Pal. N. Y., Vol. I., p. 157.) 

 MODTOLOPSIS MODIOLAEIS. 



Plate 2, fig. 17. 



Pterinea viodiolaris, Con. ; Ann. Rept. Geol. Surv. N. Y., 1838, p. 118, and 1839, p. 63. 

 Cypricardites modiolaris, Con. ; Ann. Rept. Geol. Surv. N. Y., 1841, p. 52. 

 Cypricardites ovata, Con. ; Ann. Rept. Geol. Sur. N. Y., 1841, p. 52. 

 Cypricardites ovata, Emmons; Geol. Rept. 3d Dist. N. Y., p. 405, fig. 2, 1842. 

 Cypricardites angustifrons, Emmons ; Geol. Rept. 3d Dist. N. Y., p. 405, fig. 1. 

 Modiolopsis modiolaris, Hall; Pal. N. Y., Vol. I., p. 294, pi. 81, fig. 1, and pi. 82, fig. 1. 

 Modiolopsis modiolaris, Hall; Foster and Whitney, Lake Sup., p. 214, pi. 31, fig. 2a. 



Shells of this species are not uncommon among collections of Lamelli- 

 branchiates from the vicinity of Cincinnati. They are, however, usually 

 in the conditions of casts of the interior, and present only the internal 

 characters, beyond the general outline and form of the shell. Occasion- 



