180 



In all the specimens of this north-western variety that the writer has 

 seen, the ventral valve is longer than broad, or at least as long, and its 

 beak is prominent, erect or prolonged, and narrowly conical, whereas the 

 ventral valve of Jthynclwtrema incuquivalvin, Castelneau ( = increbescens, 

 Hall) is almost always broader than long, and its beak short and 

 incurved. This variety of Rhynchonella Anticostiensis dififers from the 

 typical form of that species in being a little larger, and proportionately 

 rather broader in advance of the midlength. The eastern specimen of E. 

 Anticostiensis figured by Billings, which is as l:irge as any the writer has 

 seen from Anticosti, is 17 millimetres long, as measured along the median 

 line, and 15 mm. in its greatest breadth. Two average adult examples 

 of the north-western variety of that species, from Lower Fort Garry, 

 measure, — the one 19 mm. in length by 17'75 mm. in its greatest breadth, 

 — and the other 20 mm. in length by 20 mm. in breadth. Some of the 

 specimens from Lower Fort Garry approach rather closely to Atrypa sub- 

 trigonalis. Hall, but the antero-lateral angles of the former are more broadly 

 rounded. The characters of the interior of the typical R. Anticostiensis 

 are still entirely unknown, but casts of the interior of the closed valves 

 of the north-western variety ^hew the impression of a mesial septum, 

 which commences at the beak and extends about half way to the anterior 

 margin, in the dorsal valve. • 



Zygospira recdevirostra. Hall. (Sp.) 



Atrypa recumirostra, Hall 1847. Pal. N. York, vol. 1., p. 140, pi. 33, 



figs. 5, a-d. 

 Rhynchonella ? recurvirostra, Hall 1859. Twelfth Rep. N. Y. St. Cab. Nat.. 



Hist., p. 66. 



Rhynchonella recurvirostra, Billings 18B3. Geol. Canada, p. 168, fig. 152. 



Anazyga recurvirostra, Davidson 1882. Suppl. |Brit. Silur. Brach., p. 129. 



Zygospira recurvirostra, Winchell and Schu- 

 chert 1893. Lower Silur. Brach. Minn., p. 466,, 



pi. 34, figs. 38-41. 



Inmost or Birch Island, Kinwow Bay, Lake Winnipeg, T. C. Weston, 

 1884, three specimens ; and Big Sturgeon Island, D. B. Dowling and L. 

 M. Lambe, 1890, one specimen. 



Cyclospiea bisdlcata, Emmons. (Sp.?) 



Orthis hisulcata, Emmons 1842. Geol. N. York, Rep. Second Distr.,, 



p. 396, fig. 4. But not described. 



Atrypa hisulcata, Hall 1847. Pal. N. York, vol. I., p. 139, pi. 33, 



fig. 3. 



Gamarella bisulcata. Miller 1877. Amer. Pal. Poss. , p. 107. 



Cyclospira bisulcata, Winchell and Sohu- 



ohert 1893. Lower Silur. Foss. Minn., p. 470, pL 



34, figs. 49 54. 



