Fossils of the Calciferols SandrocTc. 



355 



quite half the width in some of the specimens and more than half 

 in others. 



Associated with the larger are others almost an inch wide, with 

 the whorls more convex below, but presenting no other differ- 

 ences so far as I have been able to observe. I think they are of 

 the same species. 



Fig. 6. 



a Pleurotomaria Laurentina. 



is a cast. 

 b — c Side views of two specimens 

 d A large imperfect cast. 



View of the spire. The specimen 



This species is allied to R. lapicida, Salter, but differs in hav- 

 ing the whorls gently convex above, and in the form of the aper- 

 ture which in that species is acutely oval, while in this it is sub- 

 rhomboidal. The outer angle of the aperture of E. Icqricida, 

 measures about 75°, but in this species it is more than 90°. 



The two species are most closely related, and it is not improba- 

 ble that intermediate forms may yet be found to connect them. 



Formation and Locality. — Mingan Islands, Calciferous Sand- 

 rock and White Limestone. 



Collector. — J. Richardson. 



Pleurotomaria gregaria. (N. s.) 

 Fig. 8— £, k. 



Description. — Shell, small ; spire conical ; apical angle about 

 45° ; whorls, three or four, with a very narrow spiral band 

 which, on the body whorl, is rather above the middle of the 

 volution, but in the upper whorls is situated on the lower outer 



