191 



least half the whole width. Surface with fine striae, which curve back- 

 wards from the suture to the margin, and then forwards to the umbilicus. 

 The specimens usually show numerous shallow undulations following the 

 course of the fine striae. 



Width of a large specimen 18 lines. 



Besides the form above described there are several others, which are 

 either varieties, or closely allied species. I propose to classify them, as 

 follows, provisionally : — 



1. P. rotundispira. — Spire not so much elevated as that of P. Que- 

 becensis, and rounded at the apex. 



2. P. Missisquoi. — About 2 inches wide ; whorls more convex, both 

 above and below. This form occurs at Phillipsburgh in the upper part 

 of the limestone. 



3. — A form with wide whorls, resembling P. Canadensis, and not 

 distmguishable therefrom in imperfect specimens. Occurs at Phillips- 

 burgh. 



All these are closely related to P. Americana, P. Progne, P. calcifera, 

 P. Canadensis, P. aperta, and many others ; different localities, appar- 

 ently, having one or more varieties. 



Locality and Formation. — P. Quebecensis and P. rotundispira occur 

 at Point L^vis in limestone No. 2, Quebec Group. 



Collectors. — Sir W. E. Logan ; T. Devine ; J. Richardson. 



Cyrtoceras Mbtellus. (N. sp.) 



Fig. 175. 



Fig. 1T5. — Cyrtoceras Metellus. Side view. 

 116.— C. Dictys. " " 



Fig. 176. 



description. — Shell gently curved ; section circular, or nearly so ; 

 septa about eighteen to the inch ; chamber of habitation proportionally 

 yery deep. Siphuucle unknown. 



