19 PALAEONTOLOGY OF NEW- YORK. 



LiiiiTula delia ( n. s.)- 



PLATE IL 



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 difiTers 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'Coy 

 ( British Palaeozoic 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 in, of the Synopsis of 

 the Palseozoic 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 n. 



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, 



