216 
PALEONTOLOGY OF NEW YORK. 
Surface oriiaiiiented by elevated lines, which are transverse and closely 
crowded near the apex, becoming strongly lamelliform and bent downwards 
over the longitudinal furrow, those toward the base not crossing this depres¬ 
sion. Where thus interrupted the lines have multiplied more rapidly than 
on the anterior portion of the valve. 
Length of the single plate 2-.5 mm., width 1.5 mm. 
Distribution. Upper Ilelderberg group. Corniferous limestone; In the 
boulders of decomposed chert, Canandaigua, Ontario county. 
Turrilepas cancellatus, n. sp. 
PLATE XXXVI, FIG. 2. 
A SINGLE plate is characterized by a few distant elevated concentric lines, 
crossed by fine, closely crowded, interrupted, radiating lines, which are more 
elevated and more conspicuous toward the posterior margin. The valve 
appears to be sinuous medially and is abruptly deflected to the left antero¬ 
lateral margin. 
The specimen is small, measuring 2.5 mm. in height and 2 mm. in length. 
Distribution. Upper Helderberg group. Corniferous limestone; In the 
decomposed chert, Canandaigua, Ontario county. 
Turrilepas Devonicus. 
PLATE XXXVI, FIG. a. 
Plv.mulites Devonicus, Claekb. Amev. Jour. Science, Third Series, vol. xxiv, p. 55, ligs. 1 and 2. 1882. 
The plates of this species appear to be of two forms; one elongate-sub- 
triangular and feather-like, the lateral margins curving to the nucleus, which is 
apical, basal margin terminal, surface fiat except for a rounded median ridge 
extending from the apex to the base, which becomes wider and stronger with 
each increment of growth along the margins; concentric growth lines elevated, 
moderately distant, curving upward and closely appressed. The other form is 
broader and oblique, with sub-equal, convex margins, and sub-apical nucleus. 
