68 CANADIAN MICRO-PALTEONTOLOQY, 



10. IsocHiLiNA Whiteavehii (sp. nov.). 



PI. 10, figs. 13 a and b. 



Length 2-0 (hinge-line 1 -6), height 1*25 (less than in the drawing), 



thickness of carapace 1 • 1 mm. 



Black, smooth, sublenticular, with straight dorsal and well curved 

 ventral border (drawn too deep in fig. 12 a), ends boldly rounded, but 

 not quite equally, the postero-dorsal angle being stronger than the 

 other ; convexity moderate, stronger in front than behind. A shallow 

 subtriangular furrow on the front third of the dorsal region. At first 

 sight it was thought to be an abnormal Frhnitia, (Quai-t. Journ. Geol. 

 Soc, vol. XLVI, p. 552). 



In general outline this specimen has some resemblance to Aparchites 

 Whiteavesii, J. (Ann. Mag. Nat. Hist., sor. 6, vol. Ill, 1889, p. 384, pi 

 xvii, fig. 10, and p. 385, woodcuts, figs. 5 and G), from Manitoba, but it 

 is more oblong, the hinder moiety extending farther backwards, its 

 hinge-line being relatively longer, and more especially there being a 

 dorsal depression, or feeble nuchal furrow, in the front moiety of the 

 valve, like that in fig. 16 a, and pi. xi, fig. 16 a ; the greatest convexity 

 (fig. 13 b) is towards the front and below the sulcus at the same part 

 of the valve as in fig. 10 b. The presence of a dorsal furrow separates 

 this form from Aparchites, and, with the absence of ventral overlap, 

 allows us to place it in Isochilina. 



In shape this approaches Primitia pusilla, J. <fe H., 1865; but the 

 latter is very small and depi-essed and has no dorsal angles. 



As a new species I name this after the eminent paleontologist of the 

 Geological Survey of Canada. 



From the Trenton Limestone of Lorette Falls, Eiver St. Charles, 

 Province of Quebec, collected by Mr. H. M. Ami in 1888. 



11. Isochilina Amii (sp. nov.). 



PI. 10, figs. 14 a, 14 b. 



Length 2-3 (hinge-line 1*5), height 1*5, thickness of carapace 1 "0 mm. 



A small black valve, ovate-oblong ; dorsal border long and straight; 

 anterior end evenly and posterior elliptically rounded ; ventral edge 

 neatly curved and obscurely crenulated. Surface marked with small 

 scattered pits ; greatest convexity at the hinder moiety. 



