Silurian Fossils of Nova Scotia, 145 



This species resembles in form the Chonetes cornuta of the 

 Clinton group of !N'ew York, but is a much larger and more ven- 

 tricose shell ; the striae are proportionally less numerous and 

 more closely arranged, the interstices being less than the striae, 

 while in the C. cornuta the interstices are wider than the striae, 

 and the latter increase only by interstitial additions below the 

 middle of the sheU. A stronijer and more elevated stria often 

 marks the median line from beak to base of the ventral valve. 



4. Chonetes tenuistriata. N. sp. Fig. 3. 



Shell semi-oval, twice as wide as long ; ventral valve moderately 

 convex, hinge line equalling the width of the shell ; surface 

 marked by fine, even, closely arranged striae, which apparently 

 increase only by interstitial additions, and are not flexuous. 

 The number of striae on the margin of the shell is nearly one 

 hundred. 



This species is more finely striated than the preceding, the 



striae not flexuous, more even, and in shells of equal size much 



more numerous. This species is somewhat larger and more 



closely striated than the C. cornuta of the Clinton group of New 



York. 



5. Spirifer rug^gosta. InT. sp. 



Shell somewhat semi-elliptical ; dorsal valve very convex, with 

 the mesial fold depressed along the centre ; ventral valve with a 

 wide deep mesial sinus ; plications six or seven on each side of the 

 mesial fold and sinus, strong, and much elevated, subangular, 

 crossed by numerous strongly elevated, lamellose, imbricating 

 concentric striae. 



The specimens examined are almost all imperfect casts, some 

 of which preserve the impression of the strong concentric striae, 

 and in one or two specimens an impression of the shell reveals the 

 streno^th of the surface markings. 



In many respects this species resembles the S. 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 New York specimens. 



6. Spirifer subsulcatus. N. sp. 



Shell semi-elliptical, hinge line equalling or greater than the 



length of the shell below ; plications five or six on each side of the 



Can. Nat. 5 Vol. Y. No. 2. 



