173 



the curvature of the ventral, its cardinal area about one mm. and a 

 quarter in height, and its beak apparently small. 



" Surface of both valves marked with very numerous and closely dis- 

 posed, thread-like radiating raised lines or minute ridges. In the only 

 well preserved dorsal valve known to the writer these radii are very 

 nearly equal in size, but upon the ventral valves of several specimens 

 they are unequal in size and irregular in their disposition. In some 

 places the larger radii alternate with the smaller ones, but in others 

 there are from two to four, or even more, of the smaller radii between 

 two of the larger ones. In addition to these radii, the visceral disc of 

 the ventral valve of some specimens is marked with comparatively coarse, 

 undulating, concentric but somewhat interrupted corrugations. 



"Hinge dentition and characters of the interior of both valves unknown, 

 but an imperfectly preserved cast of the interior of the shell of a ventral 

 valve" from Cat Head "shews that the flabellate diduotors of that valve 

 are very similar in shape to those of R. alternata, as figured by Hall on 

 Plate 8, figure 10, of the eighth volume of the ' Palseontology of the 

 State of Jfew York,' though their external margins are very much less 

 distinctly defined." 



"Apparently not uncommon " " at Lower Fort Garry — where it was 

 collected by Do aid Gunn in 1858, by Dr. R. Bell in 1880, by T. C. 

 Weston in 1884, and D. B. Dowling in 1891, and at East Selkirk — 

 where specimens were obtained by T, C. Weston and A. McCharles in 

 1884. From the limestones of Lake Winnipeg it has so far been collected 

 only at Cat Head (by T. C. Weston in 1884 and D. B. Dowling in 1891), 

 and at Jack Head Island (by D. B. Dowling and L. M. Lambe in 1890). 

 "Altogether, the writer has seen fourteen specimens of this shell, three 

 of which show the characters of the hinge area of both valves fairly well 

 though the beak of the dorsal valve cannot be seen in either, as it is 

 either broken off or buried under the matrix. The ventral asj^ect of 

 these specimens is remarkably similar to that of the fossil figured by 

 Professor Winchell and Mr. Schucherfc on Plate 31, figures 35 and 36 

 of the ' Lower Silurian Brachiopoda of Minnesota,' as Rafinesquina 

 alternata, var. lo.corhytis, but which, Mr. Schucherthas recently informed 

 the writer, he now regards as a form of R. Kingii, the Strophomena 

 Kingii of Whitfield. Mr. Schuchert, however, who has seen all the 

 specimens from Manitoba upon which thp preceding description is based, 

 states that their hinge areas are always nearly three and even four times 

 as high as those of the Minnesota specimens of R. Kingii which he has 

 studied, and regards this as a valid distinction between them. Professor 

 Whitfield, also, who has seen some of the most perfect Manitoba speci- 

 mens of R. lata, regards them as specifically distinct from his Stropho- 

 •mena Kingii, on the ground that the umbones of ventral valves of the 



