69 



GASTEROPODA. 



ScENELLA CONICA, Whiteaves. 



Scenella conica, Whiteaves. 1884. This volume, pt. 1, p. 32, pi. 5, figs. 2 & 2a. 

 " S. A. Miller. 1889. N. Am. Geol. and Palseont, p. 392, fig. 648. 



Of this species there are about a dozen specimens in the Museum of 

 the Survey, which were collected at Durham by Mr. Townsend between 

 the years 1879 and 1884. Each of these is a nearly perfect cast of the 

 interior of the shell, upon which not a vestige of the muscular impressions 

 can be detected. 



Ths genus Scenella, which was constituted by E. Billings in 1872, is 

 not mentioned in Dr. Paul Fischer's manual of recent and fossil shells, 

 by Zittel in his Handbuch der Palseontologie, nor by Nicholson in the 

 latest or any other edition of his Manual of Palaeontology. Tryon, in 

 his " Structural and Systematic Conchology," and S. A. Miller (op. oit.) 

 place it in the class Pteropoda, but its conical, limpet-like shell suggests 

 that it may rather be referable to the Patellidse or Capulidse. It seems 

 to the writer that Scenella, Palceacmea (Hall, 1873), and Hercynella 

 (Kayser, 1878) are very closely related, if not actually synonymous. 



Capulus Canadensis, Whiteaves. 



Plate 11, fig. 1. 



Tryblidium Canadense, Whiteaves. 1884. This volume, pt. 1, p. 31, pi. 5, figs. 1 & 1 a. 



The only known specimen of this species is a cast of the interior of the 

 shell, from Hespeler, which does not show the muscular impressions at all 

 clearly. Still, upon this cast there is an obscure, narrowly elliptical de- 

 pression on each side of, and at a short distance below, the nearly terminal 

 apex. These depressions seem to be united into one continuous subhemi- 

 spherical scar, under and immediately behind the presumably posterior 

 apex. This supposed muscular scar is not quite correctly represented in 

 the two figures of Tryblidium Canadense on Plate 5, of the first part of 

 this volume, and a new figure of the type specimen is given on Plate 11. 

 If the appearances just described are correctly interpreted, they would 

 seem to indicate that the fossil, now under consideration is referable to 

 the Capulidse of Cuvier rather than to the Patellidfe, though one would 

 expect to find the muscular impressions upon the cast represented by 

 slight elevations rather than depressions. Until more perfect specimens 

 are obtained, therefore, it is thought desirable to refer the present species 

 to Capulus, in the sense in which De Koninck uses that generic name, 

 rather than to Tryblidium. 



