THE CANADIAN NATURALIST. 



[Vol. X 



ence of external chambers, Billings supposed that the sheathing 

 divisions of the interior described by Salter had been filled with 

 a solid deposit of carbonate of lime, so that this curious shell 

 would seem to have had a sinker as well as a float. The speci- 

 men now to be described shows that this was probably an error, 

 and that the shell had a double series of chambers, and was thus 

 not a very simple form, as supposed by Salter, but really a shell 

 of great complexity. Billings afterwards described three addi- 

 tional species from the Quebec group of Newfoundland. 



Fig. 1. — Siphuncle of Piloceras amplum^ natural size, from a photo- 

 graph. The chambers are seen in part on the stone at the 

 lower side, but have not been correctly given by the 

 engraver. 



The present specimen was found in the Calciferous sandstone, 

 a few miles south-east of Lachute, by Mr. Macpherson, a mem- 

 ber of my class in Geology, in the course of an excursion to that 

 neighborhood last autumn. It represents a species quite distinct 

 from those described by Salter and Billings — probably an adult 

 individual — and it illustrates in a very interesting manner the 

 complex structure of this remarkable group of shells. 



