71 



the adult shell, collected by Dr. R. Bell in 1862 from rocks of about the 

 age of the Niagara limestone, at L'Anse a la Vieille in the Bale des Cha- 

 leurs ; and another but less perfect specimen, also identified, though 

 with some doubt, by Mr. Billings as this species, collected by the late 

 Mr. James Richardson in 1856 from "Division 2" of the Anticosti 

 Group, at Cape Sand Bay, Anticosti. 



Pledeotomaeia. 



The Pleurotomarise that have so far been collected from the dolomites 

 of the Guelph formation in Ontario are so imperfectly preserved that it 

 is not yet practicable to group them according to their natural relations 

 Many of the species are still known only from casts of the interior of the 

 shell, and even in those rare specimens which are partly or wholly testi- 

 ferous, the minute structures of the slit band are not preserved. Under 

 these circumstances the only course that seems to be feasible is first to 

 group together those species that are now known to have an alate or 

 spinose periphery, and afterwards to consider those apparently devoid of 

 either, in accordance with the dates at ilifhich they were described, com- 

 mencing at the earliest. 



A. Periphery alate. 



Pleueotomaeia Valeeia, Billings. 



Plate 4, figs. 1 and la, and pi. 11, figs. 2 and 3. 



Pleurotomaria Faieria, Billings, . .1865. Geol. Surv. Canada, Pal. Foss., Vol. I., 



p. 169. 

 Whiteaves.1884. This volume, pt. 1, p. 23, pi. 4, figs. 1, 

 and 1 a. 

 Probably = Pleurotomaria alata, Wahlenberg. 

 Cfr. Pleurotomaria alata (Wahl.) as figured by Lindstromiu 1884 on pi. 10, figs. 18-32 



of his Silurian Gasteropoda and Pteropoda of 

 Gotland. 



The type of P. Valeria, which was figured for the first time in the 

 present volume, is an imperfect cast of the interior of the shell, collected 

 by Mr. E. Billings at Gait in 1857. Between the years 1879 and 1882 a 

 few specimens of this species, with the test partially and imperfectly pre- 

 served, were obtained at Durham by Mr. Townsend, and one of these is 

 figured on Plate 4, fig 1 a. Two specimens from this locality are natural 

 moulds of the exterior of the apical side of the shell, and gutta-percha 

 impressions of these moulds, such as that represented on Plate 11, fig. 2, 

 show that the comparatively slender tubular portion of the outer volution 

 is encircled externally by a thin and slightly curved alate expansion, that 

 is broader than the tube itself, and shallowly concave. The correspond- 

 ing alation of the later volutions of the spire is not even indicated in either 



