167 



"This widely distributed species was first described by Shaler as 

 Orthisina diversa." A year later Billings identified it as 0. Verneuili, 

 Eichwald, at the same time regarding Shaler's species as synonymous 

 with it. On the other hand, Shaler has since referi'ed Orthisina Verneuili,. 

 Billings, to his species, in which he is correct. On comparison with the 

 European species, as illustrated by de Verneuil,* it is seen that the 

 American species is wider along the hinge-line, the ventral area much 

 less incurved and elevated, with finer strise and a narrow sinus in the 

 dorsal valve. These dififerences are sufficient to distinguish the two 

 species." Winchell & Schuchert, op. cit., p. 380. 



In the Museum of the Survey there are eight specimens on exhibi- 

 tion in the oases, which were identified with Orthisina Verneuili by E. 

 Billings, and which are still so labelled. Four of these are from the 

 Trenton limestone at Ottawa, three are from the same formation at 

 Jessup's Rapids on the Bonnechere, and one is from Division 1 of the 

 " Anticosti group " at Gamache Bay, Anticosti. All of these specimens 

 were carefully examined in 1891 by M. Friedrich Schmidt, who informed 

 the writer that the Anticosti example labelled 0. Verneuili agrees with 

 Eichwald's types of that species, but that the specimens from the 

 Trenton limestone are more like 0. Wesenbergensis, Pahlen, t and that 

 they dififer from the true 0. Verneuili. 



AnASTBOPHIA (?) HEMIPLICATA, Hall. (Sp.) 



Atrypa heiiiiplicata, Hall 1847. Pal. N. York, vol. I., p. 144, pi. 33 



fig. 10. 



K .1 Billings 1856. Canad. Nat. and Geol., vol. I., p. 



208, figs. 20-23. 



Pentamerus hemiplicatus, Billings 1859. Canad. Journ., vol. IV., p. 316. 



Hall 1859. Twelfth Rep. N. York St. Cab. Nat. 



Hist., p. 66. 



Oamarella hemiplicata, Billings 1863. Geol. Canada, p. 168, figs. 154, <c-e. 



Anastrophia (?) hemiplicata, Winchell and 



Schuchert 1893. Lower Silur. Brach. Minn., p. 382, pi. 



30, figs. 29-31. 



Deer Island, Lake Winnipeg, T. C. Weston, 1884, one adult specimen 



of a small form of this species, and J. B. Tyrrell, 1889, an apparently 



immature example. 



Steophomena incurvata, Shepard. 



Prodticta inourvata, Shepard 1838. Am. Journ. Sc. and Arts, vol. 



XXXIV., p. 144, figs. 1 and 2. 

 Orthis incurvata, Castelneau .... 1843. Essai sur le Syst. Silur. de I'Amer. 



Septentr., p. 38. 



; 



* Russia and the Ural Mountains, vol. II., pis. 11 and 12. 



+ Monogr. Orthisina. Mem. I'Aoademie de St-Petersbourg, 1878. 



