216 



PoTEBiocBRAS NOBiLE, Whiteaves. ^ 



Poterioceras noMle, Whitestves 1889. Trans. Royal. Soe. Canada, vol. VIII., 



sect. 4, p. 77, pi. 14, fig. 1. 



" Shell very large, attaining to a length of upwards of seven inches, 

 straight, subturbinate, about one-third longer than broad, and broadest 

 a little in advance of the midlength, considerably inflated but slightly 

 compressed, one side being flatter than the other, so that the outline of a 

 transverse section through the broadest part would be nearly elliptical, 

 and the'' supposed "dorso- ventral diameter about one-fourth greater than 

 the lateral. Septate portion increasing rather rapidly in size from the 

 apex", body chamber rather large, occupying more than one-third but less 

 than half the entire length, and narrowing gradually and somewhat 

 convexly to the aperture : character of the aperture unknown, though, 

 as far as can be made out in the most perfect specimen collected, it 

 appears to have been simple and entire, as well as apparently rather 

 large and subovate in outline. 



"Sutures, or outer edges of the septa, nearly straight all round, parallel, 

 and, in the specimen figured, placed at a distance of eight millimetres 

 apart at or near the (imperfect) posterior end, while the four nearest to 

 the body chamber appear to have been about fourteen millimetres apart. 

 In places where the test has been broken oflT and the cast of the interior 

 ■exposed, the septa are often seen to be coarsely crenulated. Surface 

 markings and shape and position of the siphuncle unknown. 



Dimensions of the most perfect specimen known to the writer (in 

 ■which, however, about two chambers are broken off at the posterior 

 end): — length, 177 millimetres; maximum dorso- ventral (?) diameter, 124 

 mm. ; greatest lateral diameter (approximately) about 98 mm. 



"East Selkirk, Manitoba, T. C. Weston, 1884: one I adly preserved and 

 somewhat distorted but otherwise nearly perfect specimen, and a, large 

 fragment of another, consisting of the greater part of the septate portion 

 of the shell. Lower Fort Garry, Manitoba, T. C. Weston, 1884 : one 

 very imperfect specimen, consisting also of most of the chambered portion 

 of the shell." Very large specimens, which are possibly referable to P. 

 nohile, are indicated by two worn casts of the anterior extremity of the 

 body chamber collected in 1890, the one, which is seven inches broad, 

 by Messrs. Dowling and Lambe at Berens or Swampy Island, and the 

 other, which is six inches broad, by Mr. Dowling at Commissioners 

 Island. Both are broadly ovate or ovately subcircular in a full front 

 view, and both shew the infolding of the lip, which seems to be charac- 

 teristic of the genus. 



"This species is provisionally referred to Poterioceras, on account of its 

 supposed simple and entire aperture, but it may prove to be a true 

 Gomphoceras. 



