1849.] DAWSON ON THE GYPSUM OF PLAISTER COVE. 335 



that it is with doubt he places this shell under Nerita ; the double 

 sinus appearing to indicate particular organs, which are not possessed 

 by the animals of that genus. In breaking some specimens, M. 

 Buvignier has also observed a depression under the columella, similar 

 to that which receives the apophysis of the operculum of the Nerites. 

 Locality, Launois and Yieil-Saint-Remy, Ardennes, in the upper 

 beds of the Oxford clay. 



February 21, 1849. 

 The following communications were read : — 



1. Notice of the Gypsum o/Plaister Cove in the Strait of 

 Canseau. By J. W. Dawson, Esq. 



[Communicated by the President.] 



The Strait of Canseau is a narrow passage fourteen miles in length, 

 separating Nova Scotia proper from Cape Breton Island. On the 

 Nova Scotia side it affords an imperfect section of carboniferous 

 strata, interrupted near the middle of the Strait by a mass of reddish 

 syenite and disturbed slates, forming the promontory of Cape Por- 

 cupine, which is the abrupt termination of a hilly range extending 

 far into Nova Scotia. On the Cape Breton side, the section exhibits 

 carboniferous rocks ; and nearly opposite Cape Porcupine is the small 

 indentation, whose name of Plaister Cove is derived from the mass of 

 gypsum to which the following remarks refer. 



The gypsum of Plaister Cove, like other large masses of that rock 

 occurring in this pro^dnce, belongs to the lower part of the carbo- 

 niferous system, and is associated with limestone and marls. The 

 structure and accompaniments of the bed are, however, more perfectly 

 exposed than in most of the larger masses of gypsum which I have 

 examined. For this reason I shall endeavour, with the aid of the 

 accompanying section fig. 1, and specimens, to give a somewhat de- 

 tailed view of the appearances presented at this place, A^ith the object 

 of recording facts which may be useful in explaining the origin of 

 the great beds of gypsum. 



Fig. 1. 



Coast Section at Plaister Cove. 



1 23434567 8 9 8 



1. Hard grey couglomerate. 2. Alternations of hard sandstone and grey shale. 3. Limestone. 

 4. Marl. 5. Gypsum. 6. Gypseous limestone. 7. Marl. 8. Dark shales with calcareous bands, 

 9. Brown and grey sandstone and shale. 



(1.) At APMillan's Point, about three-quarters of a mile north of 



