IO6 NEW YORK STATE MUSEUM 



the separation from this species though Professor Hall failed to identify 

 Conrad's species. Another specimen preserved as an internal cast has 

 the body longer and more slowly tapering than the rest, while the rings 

 project more at their lower ends ; this may represent a form approaching 

 C. flexuosus. 



Most of these specimens are internal casts in part retaining the wall 

 of the tube. 



No specimens of Cornulites are reported from the Guelph formation ; 

 Conrad's originals came from the Niagaran dolomite in the neighborhood 

 of Albion, Orleans co. 



OSTBACODA 



LEPERDITIA Rouault. 185! 



Leperditia balthica Hisinger, var. guelphica Jones 



Plate 21, fig. 9-1 1 



Leperditia balthica Hisinger, var. gu elphica Jones, Contrib. Canadian 

 Paleontology. 1891. pt 3, p. 80, pi. 13, fig. iza, i2b, I3a-c 



Leperditia balthica Hisinger, var. guelphica Whiteaves, Paleozoic Fossils. 

 l8 9S- v - 3. P* 2, P- i6 



Of quite common occurrence in the dolomites at Rochester are .speci- 

 mens of a large Leperditia agreeing in dimensions with the form which 

 Professor T. R. Jones has described under the name given above. These 

 are valves measuring, in the adult stage, from 10-12 mm in length, 5-6 mm 

 in hight, with long straight hinge, both angles of which are salient 

 and beyond which the curving margins of the valves extend for a slight 

 distance. The surface is smooth and quite convex, most so in front of the 

 middle ; the anterior slope abrupt, posterior gradual, the eye lobe well 

 defined. These features serve to distinguish it from L. phaseolus 

 Hisinger, var. guelphica Jones (Guelph of Ontario), which is more 

 oblique in outline, with angles not projecting and convexity more regular. 



It seems quite possible that on close comparison L. balthica 

 guelphica may be found identical with L. fonticola Hall 1 from 



'N. Y. State Cab. Nat. Hist. 2oth An. Rep't. 1867. p. 335. 



