Silurian Fossils of Canada, 



173 



length of thirteen lines ; thence to the apex unknown, but proba- 

 bly terminated at a length of eighteen or twenty lines. One side of 

 the fragment is nearly straight. No septa or siphuncle observed 

 in this specimen, but the form alone is sufficient to distinguish 

 the species from any other known in the Lower Silurian of this 

 country. Associated with the one above described was found an- 

 other fragment ten lines and a half in length. Width at aperture 

 three lines ; diameter at five lines from aperture four lines ; length 

 of chamber of habitation five lines and a half Next to the cham- 

 ber of habitation five of the septa are preserved and they occupy 

 a length of exactly five lines ; the siphuncle not visible. 



Locality and Formation. — Near L'Orignal, Trenton limestone. 



Collector. — R. Bell. 



Pragmoceras pr^maturum. N. s. 



Pig. 19. 



Ficr. 20. 



Fig. 19. — Phragmoceras prcBmaturum. Aperture of a specimen. 

 20.*-Side view of a different individual. 



Description. — Ventral aspect with the convex curvature ; dor- 

 sal aspect concave ; section oval narrowly rounded on the ventral 

 aspect; depressed convex on the sides and broadly rounded on the 

 dorsum. In the first inch and a half of the length the ventral 

 side forms a curve of which the radius is about one inch ; the re- 

 mainder of the curve to the apex unknown. The aperture is 

 broadly rounded on the dorsal side; at about one third the dor-< 

 so-ventral diameter it begins to contract ; at two thirds its diame- 

 ter its transverse width is about half its greatest width ; thence to 

 the ventral margin the sides are sub-parallel, gradually approach- 

 ing each other ; the ventral margin narrowly rounded. On a side 

 view the dorsal two thirds of the aperture is obliquely truncatedi 



