PALAEONTOLOGY OF NEW-YORK. 
Discina tullia (n. s.). 
PLATE II. 
Dorsal valve elliptical; apex excentric, elevated above the plane of the 
margins of the shell nearly one-eighth of an inch ; length half an inch, 
and breadth little more than three-tenths of an inch. 
Surface marked by fine crowded strise. 
A single specimen of the dorsal valve only has been seen, but its proportions 
of length and height distinguish it from any other species in the rocks of New- 
York. 
Geological formation and locality. In the Tully limestone near Ovid, Seneca 
county, N.Y. 
Biscina lodensis. 
PLATE II. 
Orbicula lodensis : Hall, Geological Report Fourth District, p.223. 
— — ; Vanuxem, Geological Report Third District, p. 168. 
Shell broadly oval-ovate or subcircular, narrower towards the posterior 
end. Dorsal valve very depressed -convex; apex minute, excentric, 
less than one-third the length of the shell from the posterior margin. 
Yentral valve flat towards the margins, and somewhat abruptly ele¬ 
vated at the apex ; foramen linear, extending more than halfway from 
the apex to the margin, and sometimes causing an undulation of the 
edge, or slight emargination. 
Surface finely striated concentrically by close crowded and little elevated 
strise, and, on the anterior half of the shell, by faint radiating folds or 
undulations. In partially exfoliated specimens, radiating marks of the 
vascular impressions are perceptible. Specimens rarely show the con¬ 
centric strise to be crenulated by delicate radiations, a character which 
undoubtedly existed in all perfect shells. 
In the partially exfoliated shells, the apex of the dorsal valve shows a 
