245 



Seventeen to thirty miles below Rainy Island : a large but very 

 imperfect valve, that seems also to be rather nearly related to S. Niaga- 

 rensis, but that may be distinct from the Rainy Island specimen. The 

 former is proportionally more convex, and tumid or geniculate at or 

 about the midlength, and its sculpture is slightly different from that of 

 the latter. 



Orthis, sp. indet. 



Seventeen to thirty miles below Rainy Island ; three imperfect and 

 badly preserved specimens of an apparently rather coarsely ribbed species. 



Meeistina (?) EXPANSA, Whitcaves. 

 Plate 27, figs. 6, 6 a, and 7. 



Meristina (?) expansa, Whiteaves 1904. Geol. Surv. Canada, Ann. Rep., vol. 



XIV, pt. F., p. 45. 



" Shell tumid, regularly and rather strongly biconvex, transversely sub- 

 elliptical and always a little wider than long ; front margin of the valves 

 not at all sinuated ; surface entirely devoid of any kind of ribs. 



" Ventral valve with a rather depressed though slightly prominent umbo, 

 and an incurved beak. 



" Dorsal valve with a much more depressed umbo and a smaller beak. 



" Surface markings of the exterior of the test unknown, those of its 

 exfoliated inner layer consisting of numerous, close-set and very minute, 

 concentric raised lines, as well as of a few rather distinct concentric 

 lines of growth ; structure of the test fibrous. 



" Characters of the interior of the valves unknown, though there is 

 clearly a long mesial septum in the ventral valve, and apparently a 

 similar one in the dorsal." 



Seventeen to thirty miles below Rainy Island : four comparatively 

 large and four small specimens. Ekwan River : two large specimens and 

 one small one. 



" These specimens are mere casts of the interior of the closed valves, 

 with small portions of the inner layer of the test attached to some of 

 them. It is by no means clear whether the beak of the ventral valve of 

 any of them is perforate or not. They are provisionally and very doubt- 

 fully referred to Meristina, on account of their general resemblance in 

 external form to the European M. tumida, but it ma^ be that they should 

 rather be referred to Meristella or Reticularia. They seem to differ from 

 Beticularia septentrionalis in their uniformly, transversely and broadly 

 subelliptical contour, and in the more depressed umbo of the ventral 

 valve of each." 



n 



