158 NEW YORK STATE MUSEUM 



the umbonal ridge suppressed probably by compression, the other more 

 rhomboidal in outline, with narrower, more numerous growth bands, sharper 

 umbonal ridge and more sinuous postlateral margin. In the absence of 

 intermediate forms these might be regarded so unlike as to be terms of 

 parallel rather than continuous series. 



Original description. Shell oblong or irregularly ovate; compressed or moderately 

 convex; an oblique, obscure angulation extending from the umbones to the posterior 

 angle; umbones sometimes slightly flattened by an obscure depression which descends, 

 gradually widening, to the ventral margin; beak small, closely incurved. Dorsal margin 

 straight, slightly concave or convex, parallel with the ventral margin or a little elevated 

 posteriorly, usually about one fourth shorter than the total length. Ventral margin usually 

 gently concave, but sometimes straight or slightly convex. Anterior extremity usually 

 with the lower half a little projecting and rounded, concave at the mid-hight or obtusely 

 rounded; posterior extremity, with the most projecting point at the mid-hight or a little 

 below, narrowly rounded or angular; the upper half obliquely truncated with a straight or 

 gently convex slope. 



Surface with wide sub-concentric rings of growth, the posterior edges of which are 

 abruptly elevated or sub-lamellose. These rings are usually flat, but are sometimes slightly 

 convex or concave. 



The largest specimen collected is seventeen lines in length, eight lines in hight at the 

 umbones, and nine lines high at the posterior end of the hinge line. All the others are 

 shorter and proportionally higher. In several specimens which have both valves in 

 connection, the right valve is the most convex. 



The surface of the broad growth rings is usually marked by very fine 

 concentric lines and with good preservation the umbonal slope presents a 

 series of fine radial and intersecting surface lines which are sometimes 

 exhibited from the hinge line as far as the middle of the basal margin. 

 Cypricardinia distincta is one of the largest forms of the genus 

 and is unlike the species known to us from the Oriskany fauna. It 

 approaches more nearly the species C. sublamellosa and C. c r a s s a 

 Hall of the New Scotland (Helderbergian) beds of New York.' We find 

 these shells to be quite common in the limestones. 



Localities. Everywhere along the coast at Grande Greve, Indian Cove 

 and Shiphead, 



Mytilarca canadensis Billings 



Mytilarca canadensis Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 52, 

 pi. 4, fig. 2, 2a 



Of this large species only the original examples and a single additional 

 specimen have been seen by us. It is evidently very distinct from 

 M. n i t i d a and approaches in contour the aspect of Gosseletia. 



Billings states that his specimens were from Gaspe, using the term 

 probably in the broad sense. 



Our specimen came from the upper beds at Gavey's, Grande Greve. 



'See Palaeontology of New York. 1859. 3: 267, 268, pi. 50, fig. i, 2. 



