166 Silurian Fossils of Canada 



those which are a little worn, it can be more rr less distinctly- 

 seen ; the last whorl usually drops a little below the margin of the 

 next preceding, but even in such instances the suture is not very 

 distinct. In the specimens from shaly rocks no surface markings 

 are visible, but in those from the sandstone of Anticosti, the 

 striae are distinctly visible curving backwards from the suture to 

 the margin. They are very fine in general, but there are occasion- 

 ally a few coarse ones at distances of half a line or thereabouts 

 from each other. Width from ten to fifteen lines ; height a little 

 variable; usually about three fourths of the width. 



This species is evidently allied to P. calcifera, but differs there- 

 from in having no umbilicus. 



Variety. — Associated with the specimens upon which the above 

 description is founded are several others which have the last whorl 

 on the underside obtusely angulated at about two thirds the width 

 from the outside, this angulation forming the edge of a shallow 

 concave umbilicus, about one third of the whole width of the shell 

 but which does not appear to penetrate the spire more than half 

 the depth of the last whorl. 



One of these specimens is nearly two inches wide, with the 

 strongly elevated margin forming a spiral ridge quite to the apex, 

 this character giving to the spire a more distinctly turretted aspect 

 than is exhibited by the specimen above figured. It may be that 

 these should constitute distinct species, but the fact of their hav- 

 ing been found associated together both at Lake Huron and Anti- 

 costi induces me to regard them as only varieties. 



Locality and Formation. — Cape Smith, Lake Huron ; Hudson 

 Eiver Group ; and also in the same formation at Anticosti. 



Collectors. — J. Richardson and R. Bell. 



Ophileta Ottawaensis. N, s. 



Description. — About one inch wide ; whorls four or five ; an 

 elevated sharp margin all round ; spire concave more or less de- 

 pressed below the plane of the margin ; underside of whorls regu- 

 larly ventricose; umbilicus wide, shallow, concave, exposing all 

 the whorls, occupying all the space within the outer whorl. Sur- 

 face not observed. 



Width of largest specimen seen fourteen lines ; width of last 

 whorl at the aperture five lines ; depth of same four lines ; depth 

 of concavity of spire in the centre nearly one line ; of umbilicus 

 rather more than one line. The depth of the concavity of the 



