GUELPH FAUNA IN THE STATE OF NEW YORK 57 



based on internal casts in a rather inferior state of preservation. Dr 

 Whiteaves holds this fossil to be identical with T. alpheus, and while 

 this is probably true, conclusive evidence of the exterior and apertural 

 characters of the Canadian Guelph specimens still fails us, and we have no 

 recourse except to continue the recognition of the term here adopted. It 

 has been contended that McChesney's name, Bucania chicagoensis, 

 has priority over T. alpheus, the description having been published in 

 advance of that of the latter, but it was unaccompanied by illustration at 

 its first description, and the original figure shows it to be a much larger 

 and more widely umbilicated shell. On the same plate with this figure are 

 others referred by McChesney to T. alpheus. 



Whiteaves was inclined to believe that all three may be found identi- 

 cal with T. dilatatus Sowerby, because Billings had identified a speci- 

 men from the Niagaran of L'Anse a la Vieille on the Bay of Chaleurs, 

 and another from " Division 2 " of the Anticosti group, with that species. 

 A comparison of our material with Sowerby's excellent figures and McCoy's 

 more complete description convinces us that the form in hand is distinct 

 from the Ludlow and Wenlock species, for, while the dimensions and 

 the surface sculpture appear to be alike in the two, the whorl section is 

 markedly distinct. This is evinced by the , flat dorsum of the whorls and 

 the broad but low cast of the aperture in Sowerby's figure, and by McCoy's 

 statement 1 that the section of each whorl is twice as wide as long. In the 

 specimens of T. alpheus from Shelby, the proportion of width to 

 hight is, in the inner volutions, as 3:2, in the ephebic volution however, 

 only as 5 : 4. This volution is, therefore, relatively much higher than in the 

 English form. In this character our material agrees fully with Hall's type 

 of T. alpheus. On the other hand, the single specimen which served 

 as representative of this species in Hall & Whitfield's description of its 

 occurrence in Ohio, 3 possesses lower volutions, it being described as having 

 the lateral diameter of its whorls nearly double that of the dorsoventral 



1 British Paleozoic Fossils, p. 309. 

  Pal. Ohio, 2 : 145. 



