12 COXTRIBUXIONS TO CANADIAN PALAEONTOLOGY. 



is therefore intended as the type of the species, was collected by ili'. 

 J.B.Tyrrell in 18S4 from the south bank of Knee Hills Creek, in 

 Township 29, Eange 22, west of the 4th ^Meridian. 



Ten imperfect and badly preserved ca^ts of shells which are probably 

 referable to this specie^, were collected by Dr. G. M. Dawson in ISSl, five- 

 at Eye-C4rass flat on the Old :!ilan Eiver, and five at the mouth of East 

 Arrow-wood Creek, on the Bow Paver ; ail from the St. Mary Eiver 

 Series. 3Ir. E. G. McConnell collected a similar cast on the Belly Eiver, 

 twenty-three miles above the mouth of the Waterton, in 18S1. Some of 

 the specimens collected by Dr. Dawson and Mr. McConnell, are broader 

 in front and shorter than the type, and in others the beaks are placed 

 much further forwards. 



In referring these shells to the genus Panopiea rather than to Ano- 

 donta or Unto the writer has been influenced by the following considera- 

 tions : first, that the valves gape ft the posterior end; secondly, that 

 they are slightly inec|uivalve, and lastly, that the inner ha'er of the 

 te-.t is not nacreous. The specific name is suggested liy the close 

 resemblance that the most perfect specimen presents to a narrow forra 

 of My a arenaria. 



Panop.ea ctjrta. (N. Sp,) 

 Plate 2, fig. 3. 



Shell compressed laterally, about one-fnurth longer than high, and 

 nearly equilateral ; posterior end gaping. Anterior side broad and 

 about a^ l"ng as the posterior, narrowing obliquely and convexly 

 both aljove and below, and obtusely subangular ur si.)mewhat pointed 

 fi little below the middle; posterior side alsn broad, truncated almost 

 vertically at its extremity in the right valve, but somewhat more 

 rounded in the left. Tentral margin broadly and regularly rounded, 

 most prominent in the middle; superior border descending rapidly 

 and oblicpiely in front of the beaks, at fir.->t nearly straight and hori- 

 zontal behind them, but ultimately forming an abruptl3' rounded 

 junction with the outer margin of the posterior end above ; beak of 

 the right valve very nearly centi'al, broad and moderateh' pro- 

 minent, incurved, with a :,light inclination forward; beak of the left 

 valve a little smaller and mi:ire ilepres-.ed. 



Surface marked with rather coarse and irregularlv disposed concen- 

 tric stri:e or lines of growth. Hinge teeth and muscular impressions 

 unknown. 



Length of the most pei-fect specimen known, forty-eight millimetres j 



