FOSSILS OF THE CARBONIFEROUS LIMESTONES. 



305 



with radiating ribs, about twelve in number, and becoming wider and 

 flatter toward the margin. Length about three lines. 



Fig. 109. — Cardiomorplia Vindobonensis (cast). 



Fig. 110. — Conocardium Acadianum; 

 nat. size and magnified. 



Conocardium. — A fragment of a cast of a much lai-ger species, with 

 very distinctly mai'ked scaly ribs, occurs in Mr Hartt's collection 

 from Stewiacke. 



Aviculopecten Lyelli^ n. sp., coll. J. W. D. and C. F. Hartt (Fig. 

 Ill), Windsor, Shubenacadie, etc. — Shell orbicular, as wide as long, 



Fig. 111. — Aviculopecten Lyclli. 

 I 



(a) and (h) Varieties of sculpture ; (c) hinge-line. 



narrowed behind, hinge-line equal to three-fourths the longitudinal dia- 

 meter. Left valve slightly convex, greatest convexity being just behind 

 the middle, sloping thence gradually to the border, where it is almost 

 plane ; umbo well marked, and quite strongly incurved. Ears flattened, 

 the posterior not separated from the umbo, but sloping gently there- 

 from. Anterior separated from the umbo by a narrow, steep, smooth 

 slope. Anterior ear rounded, and with a wide shallow notch under 

 it ; posterior pointed, and with its lateral margin concave. Surfiicc 

 of valves ornamented by about sixty rounded, well marked, radiating 

 plaits, separated by deep furrows as wide as the plaits. The plaits 

 increase both in height and breadth in going from the umbo to the 

 margin. They increase near the front and sides by implantation. 

 Those on the side of the valve are slightly curved; on the umbo they 

 can scarcely be distinguished. The plaits arc ornamented by numerous 

 sharp squamous processes, which appear to bo arranged in concentric 

 rows. These rows are separated by a space equal to that between 



