6 
PALAEONTOLOGY OF NEW-YORK. 
Lingula desiderata (n. s.). 
PLATE II. 
Shell robust, elliptical, convex, tbe width equal to about four-sevenths 
of the length, the greatest width being above the middle of the shell. 
Surface marked by fine and closely arranged concentric striae; the 
interior of the shell, and the cast, showing strong radiating striae. 
Length a little less than half an inch. 
The specimen is apparently a dorsal valve, which is truncate, and perhaps a 
little imperfect at the beak. In its general form it resembles L. ligea, but is wider 
above the centre and more convex, while it is larger than any specimens of that 
species in the collection. The presence of radiating strise has not been observed 
in L. ligea. Other ^specimens are required for a satisfactory determination of its 
character. 
Geological formation and locality. In the Corniferous limestone of the Upper 
Helderberg group, at Lapham’s mill, Ontario county, N. Y. 
Lingula issanm (n.s.). • 
PLATE II. 
Shell somewhat obovate, the cardinal end being narrower and rounded ; 
gradually expanding in width for more than two-thirds the length, 
becoming slightly narrower below, with the baso-lateral angles very 
abruptly rounded : basal margin nearly straight. Surface marked by 
fine close concentric strise, which are scarcely elevated above the 
smooth glossy surface. Shell thin : valves nearly flat. 
One specimen measures three-fourths of an inch in length by half an 
inch in its greatest width, while the width one-third the length below 
the posterior end is three-eighths of an inch. 
Two separate valves are all that have been seen of this species, but it differs 
sufficiently from all the others in these strata to be readily recognized, This and 
one other are the only species of Lingula, at this time known to me, in the lime¬ 
stones of the Upper Helderberg group. 
The specimens were received from Dr. R. P. Mann, of Milford, Delaware county, 
Ohio. 
Geological formation and locality. In limestone of the age of the Upper Hel¬ 
derberg limestone, in Delaware county, Ohio. 
