PALAEONTOLOGY OF NEW-YORK. 
12 
Lingula della (n. s.). 
PLATE II. 
Shell elliptical, twice as long as wide ; sides gently curving; base very 
regularly rounded; cardinal slopes abrupt, nearly straight : substance 
of the shell very thin. Surface marked by extremely fine concentric 
striae, and, below the centre of the shell, by numerous undulations, 
which are stronger on the middle and become obsolete on the sides. 
In the ventral? valves, a strongly impressed linear indentation marks the 
centre of the shell from near the beak more than halfway to the base. 
This feature is observed in the best preserved specimens seen, as well 
as in partial casts. An apparently adult specimen measures nine-tenths 
of an inch in length, and five-tenths in the greatest breadth. 
This species differs conspicuously from all others of the Hamilton and Chemung 
groups, except the L. maida , which is proportionally shorter, with more attenuate 
cardinal extremity and stronger surface strise. 
In general form, this species bears some resemblance to Lingula ovata of M c Coy 
(British Paleeozoic Fossils, PI. 1 L, f. 6), having the same slender form; but the 
sides are not so straight, and the front is more curved. It has not, however, the 
robust form of that species as represented in figure 1, Plate hi, of the Synopsis of 
the Palaeozoic Fossils of Ireland. 
Geological formation and locality. In the shales of the upper part of the Hamil¬ 
ton group, near Canandaigua lake. 
Lingula alveata (n. s.). 
PLATE II. 
Shell subelliptical; sides curving, broader below the middle, somewhat 
abruptly expanding and curving from the beak for more than one-third 
the length of the shell. 
Two separate valves examined (one of them a cast), are flat, and have a 
somewhat elevated or thickened border, extending from the beak, 
