29'2 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



PELECYPODA. 



(S.) Pteeinea lobata. (N. Sp.) 



Plate 38, figs. 1—1:. 



Shell inequivalve, compressed at the sides, though the main body of the 

 left valve, apart from the two wings, is moderately convex . marginal out- 

 line subovate, the length being about one-fourth greater than the height : 

 outer margin of the valves in adult specimens shallowly but distinctly 

 lobate. Anterior side short, its wing comparatively large, pointed and 

 projecting, and the lower part of its margin, beneath the wing, rounding 

 abruptly into the base, at least in the immature specimen represented by 

 fig. .3, but apparently somewhat produced above and sinuate below in 

 adults, as in the original of fig. 1, which shows indications also of what 

 seems to have l^een a byssal sinus, below the anterior ear of the right 

 valve. Posterior side hunger than the anterior : the outline of the foi'mer 

 not satisfactorily shewn in any of the full or even half-grown specimens 

 collected, though in the largest individual (fig. 1) it appears to be longest 

 and obtusely pointed a little below the middle, beneath which it narrfiws 

 rapidly into the base below, in two sliallowly conca\"e curves, with a 

 slight prominence between them. Posterior wing of the adult shell elon- 

 gated, its exact contour unknown, but, in the left valve of a very young 

 shell which may possibly be referable to this species (fig. 4), the posterior 

 alation is concave at its outer margin, and the posterior end rounded and 

 somewhat produced below. Beaks rather small, scarcely raised above the 

 highest level of the hinge line and placed a little in advance of the mid- 

 length. 



Central portion of each valve marked by from five to seven, usually six, 

 rounded and slightly nodulous radiating plications, which broaden rapidly 

 outward and project a little beyond tlie front margin as rounded Iciljes, 

 with a shallowly concave sinus Vjetween each pair. The .spaces lietween 

 the plications and the postei'ior wing also, are marked with narrow radi- 

 ating i-idges, and tlie concentric markings consist of numerous, more or 

 less close-set, raised lines, which seem to be most prominent on the poste- 

 rior wing of the left valve. Hinge dentition and nniscular impressions 

 unknown. 



Dawson Bay, Lake Winnipegosis, — on the south-east side, at Wliiteaves 

 Point, and on a small island between that point and Salt Point ; on the 

 south-west shore, at a small point about two miles east of the mouth of 

 Steep Rock River, and at an exposure about two miles west of Salt Point, 

 J. B. Tyrrell, LSyO : one or two imperfect and not \ery well preserved 

 specimens from each of these localities. 



Although in rathei' poor condition, these specimens are obviously \ ery 



