REVIEWS — GEOLOGICAL SURVEY OP CANADA. 467 



giants amongst their tribe as compared with later and existing forms. 

 Mere size, however, should be no obstacle to the reception of Mr. Salt- 

 er's ingenious suggestion, since there is in that respect less difference 

 between Receptaculites and the larger Nummulites, than between the 

 latter and the ordinary foraminiferous forms. A new species, R. 

 occidenfalis, abundant at Pauquette's Rapids, is described and beau- 

 tifully illustrated at the close of Mr. Salter's memoir. 



The Fourth Decade of " Canadian Organic Eemains " comprises 

 a complete and very interesting description of the Crinoids of our 

 Lower Silurian rocks, from the Chazy to the Hudson River forma- 

 tions inclusive, by Mr. Billings, Palaeontologist to the Survey. The 

 species described, of which the greater part are new, amount to 

 about fifty. The detailed description of these is very properly pre- 

 ceded by a brief essay on the history and structure of Crinoidese 

 generally, a plan not only convenient in. itself, as explanatory of 

 special terms, and in adding completeness to the work, but also of the 

 greatest assistance to the student ; more especially in a country like 

 this, where books of reference are not always procurable, and in 

 which so few public libraries exist. The length of this introductory 

 essay, and the want of its explanatory woodcuts, prevent us from 

 transferring to the pages of the Canadian Journal ; but the work 

 will necessarily be in the hands of all who take an interest in the 

 subject.* It is now very generally known, that although the greater 

 number of the ancient crinoids, as in the modern Pentacrinus, were 

 attached to the sea-bottom by a jointed calcareous stalk, a few species 

 were free or without a stalk ; and that the existing comatiolce are 

 attached in the embryonic or early condition, and free in the adult 

 state, Ail our Silurian crinoids (properly so-called) possess however 

 a many-jointed stem ; but Mr. Billings conceives, that some of these 

 were also at times free, and that they "moved about through the 

 water dragging their columns after them." He cites more especially 

 the Glyptoerinus ramulosus, in which species the column often tapers 

 gradually from about half-an-inch at the base of the cup, to half-a- 

 line at the lower extremity or supposed point of attachment ; and in 

 which, furthermore, when perfect, this lower end is always found to 

 be closely curled up " like a miniature coil of rope." Another 



• It cannot be too often repeated that these Decades, unlike the earlier publications of 

 the Survey, are obtainable through any bookseller. 



