WHITEAVES. J DEVONIAN FOSSILS OP MANITOBA, ETC. 295 



what obliquely at the posterior end and distinctly triangular in transverse 

 section : length nearly twice as great as the maximum height, and about 

 one-third greater than the maximum breadth. N'alves broader than high, 

 most prominent and strongly angulated on each of the ventral umbonUl 

 slopes, and flattened in the ventral region, the outline of which, as seen 

 ill full front view (as in fig. 7 a) is ovate cordate ; sides (see fig. 7) obli- 

 quely compressed, faintly and longitudinally depressed next each ventral 

 unibonal slope, then slightly elevated in the same direction, in such a 

 way as to form a low, rounded and obscure dorsal umbonal ridge, which 

 becomes obsolete at a short distance from the posterior end, in each valve, 

 and ultimately narrowing abruptly into the doi'sal margin. Hinge line 

 short, oblique : dorsal margin long, nearly straight, but slightly bent a 

 little in advance of the midlength, at first divergent from the anterior 

 margin at an angle of about 55° but afterwards nearly parallel with it, 

 the greatest height of the valves being at the junction of the dorsal mar- 

 gin with the truncated posterior end, which is obtusely pointed below. 

 Umbones prominent : beaks terminal, incurved and slightly recurved. 



Surface marked only with concentric lines of growth, which are rather 

 irregularly disposed. Characters of the interior of the valves unknown. 



Dimensions of the only specimen collected : maximum length, thirty-one 

 millimetres ; greatest height, sixteen mm. ; maximum breadth, twenty- 

 one mm. and a half. 



West side of Dawson Bay, at the first small point north of the mouth 

 of the Red Deer River, D. B. Dowling, 1889 ; one nearly perfect speci- 

 men. 



This interesting shell seems to be congeneric with the so-called " Car- 

 dium dhniiliatnin" of Goldfuss,* which the late Ferdinand Roemer 

 doubtfully referred to 2Iijfllns'\ and Tschernyschewj; to Myfilarca. The 

 two species may, however, be readily separated, even at a glance, by the 

 great difference in their lateral contour. 



(S.) MODIOMORPHA ATTENUATA. 



Modiomorpha af/enuata, Whiteaves. 1890. Trans. Royal Soc. Canada, vol. VIII, 

 Sect. 4, p. 96, pi. v, figs. 1 and la. (Separate copies.) 



South-east side of Dawson Bay, Lake Winnipegosis, at Whiteaves 

 Point, J. B. Tyrrell, 1889 : "one nearly perfect cast and three very im- 

 perfect casts of the interior of the shell." The specimen upon which the 



*Petref. Germ., vol. II, p, 3S4, pi. clx, fig. 14. 

 tLethoea Geognost., vol. I, Atla.s, pi. xxix, figs. .S.i, h, and ex. pi. 



J Die Fauna des Mittleren und Ober. Devon am West Abh. des Urals., 1887, Mem. du 

 Cora. Geol., vol. Ill, p. 47, pi. vii, fig. 11. 



