MARINE FOSSILS OF THE CARBONIFEROUS LIMESTONES. 279 



investigations ; but it is still incomplete, and will no douLt be much 

 modified by future investigations. In preparing it, I have been much 

 aided by the notes and collections of Mr Hartt, by specimens furnished 

 by Professor How and Mr Poole, and by tlie extensive paljeontological 

 knowledge of IVIr Billings. I shall copy Mr Davidson's descriptions 

 of the Brachiopoda, and shall give as many figures as possible, to aid 

 students and collectors, and to facilitate comparisons with the fossils 

 of other countries. 



Before proceeding to give the list of these fossils, there are two 

 important geological questions in relation to them which must engage 

 our attention. The first is the possibility of dividing the marine lime- 

 stones of the Carboniferous period into different stages or sub-forma- 

 tions. The second is the precise geological and geographical relations 

 of the fauna. 



With regard to the first of these points, I have myself indicated the 

 possible division of the Lower Carboniferous limestones into an upper 

 and lower series, and also the fact of some of the species extending 

 their range to the Upper Coal formation. But Mr Hartt has gone 

 into the subject much more minutely, and I shall give, in the first 

 place, a summary of his results, in connexion with my own. 



In the section at Windsor above referred to, several limestones 

 appear ; but owing to faults and bends of the beds, their precise rela- 

 tions to each other are not very evident ; still an approximation to 

 these can be obtained ; and I believe that the order given below will 

 be found in the main to be an ascending one — each limestone being 

 separated from those next it by a considerable thickness of sandstone, 

 marl, or gypsum. 



(a.) Lunestone of Avon Bridge (Avon Limestone, Hartt) — Spirifer 

 Limestone. A thick band of compact, laminated, oolitic, and brecciated 

 limestone, not highly fossiliferous, but containing Productus cora 

 (var. Nova Scoticus, Hartt) — Spii'ifer glaber, S. octoplicatus(f'), Rhyn- 

 chonella Ida., Ph'dVpsia and Bakevellia, and an Area-like shell which I 

 have not seen elsewhere [A. punctifer). This is a very thick and im- 

 portant scries of beds, and appears to correspond w4th the lowest 

 Carboniferous limestone as seen in other localities. 



(6.) Limestone, laminated, oolitic, compact, and concretionary — 

 Crinoidal Limestone. Abounds in fragments of crinoids, minute shells 

 of a Denfalina, Serpidites, and small Gasteropods, especially species of 

 Plenrotoviaria. Bakevellia antiqua also abounds in it, and it is a re- 

 markable repository of minute shells, many of which are yet undoi>cribed. 

 A limestone similar to this exists apparently in a similar position on the 

 Shubenacadie Kivcr. 



