Lower Silurian Fossils of Canada, 



2m 



ARTICLE XXXIII. — On some of the Lower Silurian Fossils of Canada. 

 The following arc some of the most common Fossils which occur in the 

 Lower Silurian Rocks of Canada : — 



Fig. 1. — Stropliomena filitexta, (Hall.) 

 The above figure exhibits the dorsal or convex valve of a very fine shell 

 which occurs in the Trenton Limestone in great numbers at Little Chaudiere 

 Falls, near the City of Ottawa,— at the 4th Chute of the Bonnechere, in the 

 County of Renfrew, and at the lower end of the Allumette Island, opposite 

 the Township of Westmeath, in the same county. 



This species is of a semi-oval shape, and regularly convex or rounded 

 from near the centre of the dorsal valve the highest point being a little 

 nearer the hiu2:e line than the centre. The ears are somewhat deflected or 

 flattened. The ventral valve is regularly concave. The area is very large 

 on the ventral valve, and the foramen nearly closed by a deltidium. The 

 area is small on the dorsal valve. The surface is covered w^ith fine rounded 

 striae crowded close together, and crossed by fine concentric lines. In some 

 specimens in our possession which appear to belong to this species, there 

 are coarser striae at regular intervals, with six or seven of the smaller ones 

 between. 



Fig. 2. — Strophomena filitexia, interior of ventral valve. 



Fig. 2 shews the large " saucer-shaped" muscular cavity which form.s 

 the distinguishing character of the genus Strophomena. In the specimens 



