172 



-mouth, and at the Limestone Rapids, one hundred miles up, by Dr. R. 

 Bell in 1879. 



Rapinesquina Leda, Billings. (Sp.) 



Strophomena Lcda, Billings 1860. Canad. Nat. and Geol., vol. V., p. 55. 



1862. Geol. Surv. Canada, Pal. Toss., vol. 



I, p. 120, figs. 98 and 99. 



Brachyprion Leda, Shaler 1865. Bui. Mus. Comp. Zool., Cambridge 



(Mass.), vol. I., p. 63. 



n Hall and Clarke 1892. Pal. N. York, vol. VIII., (Brachio- 



poda 1), p. 288, fig. 21. 



One fairly characteristic ventral valve of the typical form of this species 

 was collected at Deer Island, Lake Winnipeg, by Mr. J. B. Tyrrell in 

 1889. The following remarks upon this rather peculiar shell are made 

 by Messrs. Hall and Clarke, on page 288 of the eighth volume of the 

 Palasontology of the State of New York : " There is a small number of 

 species, the incipient members of the genus Stropheodonta, in which the 

 delthyrium is open, or but partially covered, as in some of its later forms, 

 the crenuiations are confined to a very limited extent on either side of 

 the deltidium, and upon one of these forms, Strophomena Leda, Billings, 

 from the Anticosti group. Professor Shaler has proposed to found the 

 genus Brachypeion. To the same group belong the Strophomena Philo- 

 onela, Billings, from the Pentameriis oblongus beds of Anticosti, and 

 Professor Shaler has described two other species from Anticosti, Brachy- 

 prion ventricosum and B. geniculatum. These features can scarcely be 

 regarded as of generic value, but the group is an interesting one on 

 account of its being the precursor of the fuller development of those 

 characters upon which the genus Stropheodonta was originally founded." 



Rapinesquina lata, Whiteaves. 



Plate 19, figs. 2-5. 



Rafinesqaina lata, Whiteaves 1896. Canad. Rec. Sc, vol. VI., p. 392. 



" Shell large, adult specimens measuring as much as three inches along 

 the hinge line, deeply concavo-convex, much broader than long, and 

 broadest at the hinge line : cardinal angles produced. Ventral or pedicle 

 valve strongly convex exteriorly, usually regularly arched from back to 

 front, most prominent and in some specimens gibbous and even obtusely 

 subangular about the midlength, with the visceral disc flattened obliquely, 

 in others most tumid in the umbonal region posterior to the midlength, its 

 beak moderately prominent, its cardinal area wide and about four milli- 

 metres and a quarter in height, with a broadly triangular deltidium in 

 the centre. Dorsal or brachial valve deeply concave, closely following 



