176 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



Ctprina sttbtrapeziformis, Whiteaves. 

 Plate 24, figs. 2, 2a and 2b. 



Cyprina subtrapezi/ormis, Whiteaves. 1SS7. Geol. and Nat. Hist. Surv. Can., 

 Ann. Rep. N. Series, vol. II, p. 155 E. 



Shell small, inequilateral, transversely subtrapezoidal : valves mode- 

 rately convex, most prominent on the posterior umbonal slopes, which 

 are subangular : height (in the centre) one third greater than the 

 maximum breadth : length a little more than one fourth gi'eater than 

 the height. Anterior side short and qvenly rounded : posterior side 

 about three times as long as the anterior, its extremity obliquely 

 truncated above and somewhat bluntly pointed below: superior border 

 descending rather abruptly in an obliquelj^ convex curve in front of 

 the beaks, and nearly straight and parallel with the ventral margin 

 behind them: umbones swollen lateral! j', but scarcely prominent: 

 beaks small, appressed and slightly depressed, placed about half-way 

 between the centre and the anterior margin : lunule none : posterior 

 area subangularly inflected, but very indistinctly defined: ventral 

 margin nearly straight for the greater part of its length, but rounding 

 up abruptly at the anterior end and forming an obtusely subangular 

 junction with the posterior mai'gin behind. 



Surface marked with rather coarse concentric linos of growth : test 

 somewhat thin. Anterior muscular impression subovate : posterior 

 muscular impression rather larger and more nearlj^ circular: pallial 

 line simple and entire : hinge dentition unknown. 



Dimensions of the most perfect specimen collected : maximum 

 length, twenty-three millimetres and a half ; greatest height, fifteen 

 mm ; approximate thickness through the closed valves, ten ram. 



Battle Eiver, Township 46, Eange 4, west of the 4th Principal 

 Meridian, 1885: apparently abundant. About thirty specimens were 

 collected at this locality, but of these, only one is quite perfect, with 

 the whole of the test proscj-ved, while the rest are for the most part 

 little more tharj mere casts of the interior of the closed valves, with 

 portions of the exfoliated test adherent thereto. 



The hinge dentition being unknown, it is uncertain to what genus 

 this shell should be i-eferi'cd. It may pi'ove to be a Cypricardia or a 

 Veniella i-ather than a Cyprina. 



