342 THE CANADIAN NATURALIST. [Yol. ix. 



Rhi/nchoneUa, sp. 



In the upper bed of iron ore one of the most freqnent shells is 

 a simply ribbed Rhynclionella, somewhat resembling Rh.vellicata 

 of Hall, but too much distorted and too imperfectly preserved to 

 enable it to be determined with certainty. 



Discina, sp. 



A small elevated smooth Discina, marked only with very- 

 delicate lines of growth and near in form to the more elevated 

 varieties of Z>. oblongata, Portlock, from the Middle Silurian of 



England. 



Megamhonia cancellata, Hall. 



Perfect specimens of this beautiful little shell show that the 

 right valve is flatter than the left, and destitute of the cancel- 

 lated markings, having only concentric lines. When the valves. 

 are closed the basal sulcus has very much the aspect of a byssal 

 aperture. These characters would ally this shell with AvicuUdce 

 rather than with Arcadce. 



Avlcula lameUosa, n. s, 

 Hino;e line somewhat lon2;er than the breadth of the shell, and 



DO J 



about equal to its length. Left valve tumid, right valve less so, 

 umbones appressed, base broadly rounded, anterior wing short? 

 but decidedly separated from the body of the shell, posterior 

 wing much larger. Surface smooth, but ornamented with concen- 

 tric thin raised lamellae, which are continuous over the wings 

 and body, and are elegantly waved, becoming distant from each 

 other on the lower side. Largest specimen 3 centim. long, 3 6 

 broad. At first sight this species resembles A. equilatera of Hall,, 

 but is quite distinct in form and markings. 



Aviada, sp. 



A single left valve of a well-characterised species with the an- 

 terior wing nearly as broad as the posterior, and both flat and 

 smooth, or with microscopic concentric lines on the posterior one 

 Body of the shell with about 15 radiating ribs, crossed by obscure 

 concentric ridges. I had at first regarded this shell as a variety 

 of A. Honeymani of Hall, but the anterior wing, when exposed^ 

 showed it to be altogether different. I find it difficult to dis- 

 tinguish the last-named species from A. emacerata of Hall, as 

 some specimens show radiating striae on the posterior wing, and 

 otherwise approach to that species. 



