IOSSILS. 597 



on each side of the mesial fold and .sinus, strong;, and much derated 

 gubangular, crossed by numerous strongly elevated, lamellose, imbri« 



eating concentric stria?. 



The specimens examined are almost all imperfect some of 



which preserve the impression of the strong concentric stria-, and in 

 one or two specimens an impression of the shell reveals the strength 

 of the surface markings. 



In many respects this species resembles the 8, perlamellosa of the 

 Lower Helderberg group in New York, but the mesial elevation of this 

 species is flattened or depressed, a character never observed in N< w 

 York specimens. Arisaig, East River, coll. J. W. D. 



Spirtfbr subsulcatus, Hall. Shell semi-elliptical, binge-line equalling 

 or greater than the length of the shell below; plications five or six 

 on each side of the mesial fold ; mesial fold somewhat flattened or 

 very slightly rounded on the summit ; plications rounded ; surface 

 concentrically lamellose. 



The specimens are all casts, or impressions of the shells. 



They bear some resemblance to S. sulcatus of the Niagara group, 

 and are intermediate between that species and the S. cycloptera of the 

 Lower Helderberg group. Arisaig, East River, coll. J. W. D. 



Spirifera, resembling 8. cycloptera, but with regular ribs. East 

 River, coll. J. W. D. 



Strophomena profunda, Hall. Arisaig, coll. J. W. U. Dalhousie, 

 Professor Bailey. 



S. rugosa. Arisaig. 



5. flat striated species. East River, coll. J. W. D. 



S. corrugata, Conrad. Arisaig, coll. J. "W. D. 



T7'emastospira Acadia?, Hall (Fig. 201). Shell wider than long; 

 beak of the ventral valve produced and incurved ; mesial depression 

 marked by a small fold on each side, which originates about one-third 

 of the length below the beak and continues to the margin ; sinus 

 bounded on each side by a more strongly elevated plication, beyond 

 which are six other plications on each side. Surface marked by fine 

 concentric stria;. 



This shell is referred to the genus Trematospira from external 

 characters alone, which are unlike Rhynchonella proper, and the shell 

 is not a Spirifer. Arisaig, coll. J. W. D. 



lihynchospira sinuata, n. sp. Shell ovoid, ventricose beak of the 

 ventral valve incurved; a mesial sinus beginning a little below the 

 beak; surface marked by about eight or nine simple scarcely sub- 

 angular plications on each side of the mesial sinus. 



Surface marked by concentric lines of growth. 



