220 THE CANADIAN NATURALIST. [Vol. vi, 



seen, but appear to be formed on the same plan as those of the 

 ventral valve of the genus. 



The above description is drawn up on one exterior, and 

 several interiors of the same valve, apparently the ventral valve. 

 The exterior is very like that of 0. desquamata, and is of the 

 same size, but the interior shows it to be an entirely distinct 

 species. 



Length of the largest specimen seen, seven lines ; width about 

 the same, or slightly less. 



Occurs at Trois Pistoles. Collected by T. C. Weston. 



Platyceras prim^vum. — Shell minute, consisting of about 

 two whorls, which as seen from above are ventricose, but most 

 narrowly rounded at the suture ; the inner whorl scarcely elevated 

 above the outer. The under side is not seen in the specimen. 

 Diameter, measured from the outer lip across to the opposite side, 

 one line ; width of last whorl at the aperture, about one-third of 

 a line. 



Collected at Bic by T. C. Weston. 



(Proposed new genus of Brachiopoda.) 

 Genus Monomerella, N. Gt. 



Generic characters. — Shell unarticulated, ovate or orbicu- 

 lar; ventral valve with a large area and with muscular impres- 

 sions like those of Trlmerella. Dorsal valve with muscular 

 impressions in the central and posterior portion of the shell, 

 nearly like those of Oholus. In the ventral valve there is only 

 a single septum, which extends from the cardinal line a greater 

 or less distance forwards. There are two cavities in the shell 

 beneath the area. In the dorsal valve there are no cavities in 

 the shell. The main difference between this genus and Trime- 

 rella are. thus, as follows : — 



Trimerella. — Cavities in both valves. 



Monomerella. — Cavities in the ventral valve but none in the 

 dorsal. 



The above description is intended to be merely introductory. 

 As Mr. D.ividson will soon fully describe and illustrate the genus 

 from both Canadian and Swedish specimens, no more need be 

 said about it here. 



This genus was discovered in the spring of 1871, at Hespelar, 

 Ontario, in the Guelph limestone, by T. C. Weston. Before 



