EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 159 



Mytilarca nitida Billings 



Plate 23, figures 14, 15 



Mytilarca nitida Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 53, 

 fig. 22, 23 



Orii^inal dcscripiion. Cast of the interior ovate; anterior side gently concave in tlie 

 upper two thirds, slightly convex below; posterior side broadly and gently convex, a small 

 portion next the beak (indicating the hinge line), straight. Base nearly uniformly rounded. 

 Umbones moderately jjrominent, obscurely carinate or narrowly rounded. Beak small, 

 closely incurved, almost in contact, slightly turned forwards. Between the beaks there is 

 a short straight hinge line, which forms an angle of a little less than 90° to the anterior 

 side. The outline of the anterior side is elongate, ovate; rounded at the apex; the sides 

 most prominent a little above the middle; thence narrowing to a point at the base. The 

 posterior side of the cast has a compressed margin, about two lines wide at the end of 

 the hinge line, gradually becoming obsolete towards the base. On the anterior side, 

 beneath the beaks, tiiere is a concave space which dies out before reaching the middle. 

 About one line below the beaks there is an obscure projection, indicating the anterior 

 extremity of the hinge line. 



The surface shows a few obscure concentric lines and faint radiating grooves. These 

 latter, although api)arent on the cast, may not occur on the surface of the perfect shell. 



'i'his species differs from M. canadensis in having only a small portion beneath 

 the beaks depressed, while that one has nearly the whole of the anterior side concave. 

 Hight of the largest specimen collected, twenty-one lines; width a little below the middle, 

 thirteen lines; depth of both valves, twelve lines; length of hinge line, six lines. 



Locality and formation. Indian Cove; Gaspe limestone, no. 8. 



This is more common than the preceding species and is not unlike the 

 M e g a m b o n i a o v a t a Hall of the New Scotland fauna. 



Localities. Grande Greve and, according to Billings, Indian Cove. 



Palaeopinna flabellum Hall 



PLite 21, figures 1-5 

 See p. 107 



Palaeopinna flabella Hall. Palaeontology of New York. 1884. v. 5, pt i, 

 p. 240, pi. 87, fig. 4 



It is singular that this rare species in the New York Oriskany known 

 only by a single specimen from the sandstone of Schoharie should prove to 

 be not uncommon in the Gaspe limestones. Before us is a number of 

 specimens of various sizes all showing the characters of the original and 

 exhibiting particularly the nature of the surface ornament. This consists 

 of concentric growth lines which are sharply defined over the anterior 

 and median parts of the shell but posteriorly are crossed by radial lines 

 becoming stronger toward the hinge line and eventually broken up into 

 series of radial asperities. Anteriorly the shells are abruptly bent inward 

 but do not gape, the anterior surface beneath the beak being vertical or 

 concave. Hall described this as a gape in the valves which it appeared to 

 be from his single specimen. 



