304 CONTRIBUTION'S TO DAXADIAX PAL^.ONTOLOP.Y. 



\va\- between the beaks and the postero-basal margin. Anterior side short, 

 its margin regularly rounded : posterior side much longer than the ante- 

 i-ior, its extremity obliquely subtruncated above and narrowly rounded 

 belcjw ■ \-entral margin gently convex anteiiorly and nearly straight but 

 slightly ascending posteriorly : cardinal margin curving very abruptly 

 downward in front of the beaks, nearly straight, with a slight downward 

 declination, behind them, and ultimately cur\'ing obliquely and rapidly 

 downwai-d and outward posteriorly : umbones depressed and compressed : 

 beaks small, incurved, with a forward inclination, placed near the anterior 

 end but not quite terminal. 



Surface markings and muscular impressions unknown. In the specimen 

 figured, which is the oast of the interior of a left valve, the existence of 

 a long and thin lateral tooth in that valve seems to be indicated by a nar- 

 row longitudinal grove which runs parallel with and close to the cardinal 

 margin for the whole of its length behind the beaks. 



Length of the left valve figured, sixteen millimetres : greatest height of 

 the same, ten mm. 



Devils Point, Lake Winnipegosis, J. B. Tyrrell, 1888 : a. single but very 

 perfect cast of the interior of both valves, which are widely open and 

 partially detached. 



This little shell seems to be very closely related to the Anodonlopnis 

 cfinciui/a of the Guelph limestone of Ontario*, but the valves of the 

 former are much narrower in proportion to their height, more pointed 

 posterioi'ly, and their posterior umbonal slopes are much less distinctly 

 angulated. 



(S.) Pakacvclas antiqua, Groldfu.ss. (Hp.) 



Plate 39, fig. (i. 



Lvriiia aiiliqva, Ooldfiws. 1K34-4(I. Petief. Germ., vol. II, \>. 2'2(i, pi. oxlvi, tif{S. 

 7a, b. 



iJevils Point, Lake Winnipegfjsis (three speoiniens) ; also in the Strin- 

 gocephalus zone at Dawson Bay, on the same lake, on the south-west side, 

 tw<i miles west of Salt Point (one specimen), on the west .side, at the 

 mouth oi Steep Rock River (three specimens), and at the first small point 

 north of the Red Deer River (one specimen) : J. B. Tyrrell and D. B. 

 Dowling, 1889. 



Seven (if these specimens are well defined moulds of the exterior of the 

 closed valves and one is a cast of the interior. The figure is taken from 



* Geol. and Nat. Hist. Surv. Canada, Pal. Foss., vol. Ill, (pt. 1.) ji. 12, iil. ii, fig. 

 4, and pi. vii, figs. 4 and 4a. 



