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NEW YORK STATE MUSEUM 



the umbilicus, which appears relatively large on internal casts but as indi- 

 cated by casts of the exterior was actually very small, the shell being con- 

 siderably thickened along the umbilical edge. Aperture but little expanded 

 laterally, broadly triangular reniform, outer lip with a shallow sinus, inner 

 lip not observed. Surface ornamentation not sufficiently known, apparently 

 consisting only of growth lines. 



Horizon. Lower Shelby dolomite. 



As Whiteaves reports this species from the Guelph at Gait and from the 

 Niagaran formation at Grimsby Ont., it suggests itself that also in Canada 

 this form may appear in an early manifestation of the Guelph fauna, as 

 in New York. From B. tuber Hall, the only other species of Bellerophon 

 described from the Niagaran, B. shelbiensis differs in the laterally more 

 expanded aperture and the deeper sinus of the outer lip. We have no 

 record of the occurrence of other species of true Bellerophon in the Ameri- 

 can Niagaran ; and, in view of the large representation of the genus in the 

 Lower Siluric and Devonic, it is evident that the facies in which this genus 

 flourished in Niagaran time has not yet been brought to notice. 



Though this shell was identified by Billings and Whiteaves with a 

 species of Bucania, we feel justified in referring the form to Bellerophon. 

 In the differentiation of Bellerophon and Bucania, the character of the sur- 

 face sculpture is considered by various writers (de Koninck, Waagen, 

 Koken) of critical importance ; and this feature is not clearly exhibited in 

 the Shelby material, but the character of the umbilicus, and of the section of 

 the whorls is distinctly bellerophontid. The umbilicus has been described 

 above ; and the section is not flat on the dorsum and angulated at the edge, 

 as in the generic type of Bucania, but rounded and embracing with the edges. 

 All through the literature of paleozoic gastropods the distinction of Hall's 

 genus Bucania from Bellerophon has been involved in much uncertainty 

 and doubt. Professor Hall did not originally define the genus sufficiently 

 to avoid misconception. It seems evident that, as suggested by Koken and 

 Ulrich, Hall used B. expansa as type of his genus, but, as he described 

 B. sulcatina as the first species of the genus, this had to be taken as 



