48 



There are sometimes one or two obscurely developed ribs at the cardinal 

 angles, so that the number of the ribs may be, for the dorsal valve, five, 

 seven or nine ; and for the ventral valve, six, eight or ten. Specimens 

 occur with the mesial fold greatly elevated and produced forwards, form- 

 ing a strong projection in the middle of the front margin. 



Some of the exfoliated specimens exhibit from one to three lar^-e 

 rounded knobby projections on some or all of the ribs. 



Localitt/ and Formation.— GrsLud Greve, Gaspe ; Gaspe limestone, No 

 8. It occurs in the Corniferous in Ontario, and in the same formation in 

 the State of New York. 



Collector — R. Bell. 



Spirifera cycloptera. (Hall.) 



Plate 3 A, figs. 4, 4a, 4b, 4c. 

 Spirifer cyclopterus. (Hall.) Pal. N.Y., vol. 3, p. 199, pi. xxv, fig. l,a—z. 



Description. — Sub-semicircular ; varying from moderately to rathe 

 strongly convex ; in a view of the hinge-line the outline of the two valves 

 is lenticular ; cardinal angles either rounded, rectangular or slightly 

 acute ; outline of the front half broadly rounded, a portion in the middle 

 slightly concave or projecting. Ventral valve usually the most convex, 

 greatest depth a little above the mid-length ; compressed at the cardinal 

 angles ; umbo and beak small, the latter incurved, sometimes nearly in 

 contact with the dorsal umbo ; area small, about one line high in a 

 specimen sixteen lines wide, concave, not extending quite to the cardinal 

 angles. The mesial sinus is concave, its width at the front margin equal 

 to about one-fourth of the whole width of the shell ; it extends to the beak. 



Dorsal valve generally not so convex as the ventral ; mesial fold round- 

 ed ; area small, in the plane of the lateral margin ; umbo on a side view a 

 little elevated above the edge of the area ; beak scarcely distinct, closely 

 incurved. 



A large specimen, sixteen lines wide,has eight moderately convex rounded 

 ribs on each side of the mesial fold and sinus ; two of these at the cardinal 

 angles are obscurely developed. Smaller individuals have only five or 

 six ribs. The surface has, to the naked eye, usually a smoothish aspect, 

 but when perfect is seen to be covered with concentric sub-lamellose 

 striae, "which are crossed by very fine longitudinal striae, giving a minutely 

 fimbriated appearance. 



The size varies from five to eighteen lines in width. 



