216 PALEONTOLOGY OF NEW YORK. 



Surface ornamented 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 

 mi the anterior portion of the valve. 



Length of the single plate 2.5 mm., width 1.5 mm. 



Distribution. Upper Helderberg 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. 3. 



Plumulites Deixmwus, Clakke. Amer. Jour. Science, Third Series, vol. xxiv, p. 55, figs. 1 and 2. 1882. 



Tin; plates of this species appear to be of two forms; one elongate-sub- 

 triangular ami leather-like, the lateral margins curving to the nucleus, which is 

 apical, basal margin terminal, surface flat except for a rounded median ridge 

 extending from the apex to the base, which becomes wider and stronger with 



ch 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, 



