132 CONTRIBUTIONS TO CANADIAN PAL.5;0NT0L0GT. 



long. 122° 10', A. R. C. Selwyn, 1875. Fossil Eidgc, Upper Pine Eiver, 

 in lat. 55° 30' and long. 122°, J. Hunter, 1877. Whipsaw Creek, head, 

 waters of the Similkameen, Dr. Gr. M. Dawson, 1877: a few obscure 

 specimens, which are referred to this species with some doubt. South 

 side of Skidegate Channel, Q.C.I., a mile and a half west of Log Point; 

 G. M. Dawson, 1878. 



The specimens, though characteristic and easily recognisable, ai'c for 

 the most part imperfect, except those from the locality first mentioned. 

 Among these latter there are several nearly perfect and well-j)reserved 

 right valves, two of which are represented on Plate 17, as only the 

 left valve of M. subcircularis has been figured bj' Mr. Ciabb. 



The spiecimens from British Columbia are as often obliquely sub- 

 ovate and longitudinally elongated as subcircular in outline, but the 

 "rounded upper end of the anterior margin," which Mr. Gabb states 

 is the " most obvious ditt'erence between his species and M. salinaria," 

 apipears to be a constant character of the former. 



In his memoir on the Arctic Trias Fauna, Mojsisovics expresses the 

 opinion that M. subcircularis belongs to the genus Fseudomonotis of 

 Beyrich, and that it is probably identical with P. ochotica. The sj)eci- 

 mens of M. subcircularis collected by Dr. Selwyn on the Peace Eiver 

 certainly bear a very close resemblance, both in general form and in 

 sculpture, to some of Mojsisovics' figui'os of P- ochotica, but in these 

 figures both valves and more especially the right valves are repre- 

 sented as provided with a minute and spine-like anterior auricle the 

 existence of which is not satisfactorily shewn in any of the Canadian 

 specimens. 



MONOTIS OVALIS. (N. Sp.) 



Plate 17, fig. 4. 



Left valve (the only one known) compressed, but moderately tumid 

 in the umbonal region. General outline rather broadly subelliptical 

 but slightly inequilateral: height about one-fourth greater than the 

 length: cardinal margin very short. 



Anterior side a little shorter than the posterior, its margin much 

 less convex and neaidy straight and vertical or slightly sinuous above 

 the middle : posterior margin regularly and broadly rounded : pallial 

 border also regularly but narrowly rounded. Superior border sloping 

 obliquely, convexly and rapidly downward behind the beak, higher 

 and nearly straight for a short distance immediately in front thereof: 

 anterior cardinal angle less broadly rounded off than the posterior: 



