49 



Locality and Formation, — Grand Greve, and Indian Cove, Gasp6 

 No. 8. Also at the Split rock, Perc^. In the State of New York, it occuri 

 in the shaly limestone of the Lower Heldcrberg Group. 



Collector.— Ji. Bell, T. Curry. 



Cyrtina affinis. (N.sp.) 



Plate 3 A figs. 6, 6a, Sb. 



Description, — Ventral valve sub-pyramidal, the apex sometimes more 

 or less twisted ; mesial furrow angular at the apex, becoming sub-angular 

 below and sometimes rounded at the basal margin. On each side of tho 

 mesial furrow there are five or six ribs, those next the mesial furrow the 

 laro-est, the others becoming smaller and more obscure outwards. On 

 most of the specimens there are several concentric striae. The area is 

 large and concave, its height equal to about half the width of the shell at 

 the hinge-hne. The deltidium is convex, at the base equal to one- fifth the 

 width of the shell ; an aperture near the apex in some, if not in all, tho 

 specimens. This aperture is sometimes not visible. The area is transverse 

 ly striated. 



Dorsal valve gently convex, a strong rounded median rib, with five or 

 six on each side. This valve is nearly semicircular, its length being nearly 

 half its width on the hinge-line. 



In 1863, 1 discovered the spiral coils in this species, and gave an 

 account of them in the Canadian Naturahst, vol. 8, p. 37. I then sup- 

 posed it to be C. Dalmani^ Hall. As the specimen has since been damaged^ 

 so that the structure of the coils cannot be seen, I shall here copy what 

 was pubHshed at the time ; 



" Mr. Davidson in his Monagraph on the British Carboniferous Brachiopoda, p. 68 

 points out, that no spiral coils had been noticed in the genus Cyrtina by any author. By 

 working at some silicified specimens with acid, I have been so fortunate as to discover 

 these organs in two species. Their position is the same as in Spirifera, but the first two 

 coils are (at least in one of the species, C. Dalmani, Hall) connected a little in front of tho 

 mid-length by an apparatus somewhat like that of Spiriyera, but not so complicated, A 

 very slender process springs upwards towards the ventral ',valve, from each coil, and, at 

 the height of about one line, curves forwards. The two then unite and form a single band, 

 which extends forwards to about the front of the coil, and there ends in an obtuse point," 



The dorsal valve of this species has two small projections between the 

 dental sockets, somewhat like the divaricator processes of a Stropliomena, 

 Width of largest specimen seen, one inch ; height of area, six lines. 

 Locality and Formation, — Grand Greve, Gaspe. No. 8. 

 Collector. — R. Bell. 



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