220 



sides compressed, somewhat expanded, especially at the midlength and 

 anteriorly; chamber of habitation occupying about one-third of the entire 

 length, which latter is more than twice but less than three times the 

 maximum breadth ; outline of transverse section, in the thickest part, 

 elliptical, with the longer axis of the ellipse not quite twice the length of 

 the shorter ; surface showing indications of fine transverse costse, though 

 the exterior of the test is not very well preserved. Septa rather closely 

 approximated and averaging about three millimetres apart ; siphuncle 

 nearly marginal, moniliform, and slightly inflated between the septa, the 

 maximum breadth of each siphuncular segment being one-third less than 

 its height or depth." 



Approximate dimensions of the only specimen known to the writer : 

 length, eighty-six millimetres; greatest breadth, thirty-three mm.; maxi- 

 mum diameter at a right angle to the breadth or length, nineteen mm. 



Little Black Island, Lake Winnipeg, D. B. Dowling and L. M. Lambe, 

 1890: one specimen, which is almost if not quite equilateral in its broad- 

 est aspect. 



Oncoceras magnum, Whiteaves. 



Onrnccruii jiutgnuvi, Whiteaves 1889. Trans. Royal Soc. Canada, vol. VII., 



sect. 4, p. 79, pi. 15, fig. 1. 



Shell large, slightly compressed, somewhat fusiform and contracted at 

 both ends, but convexly curved, prominent, tumid and gibbous near the 

 midlength, on the antisiphonal side, and nearly straight on the opposite 

 or siphonal side; outline of transverse section in the thickest part broadly 

 elliptical or subovate. Septate portion broadening rather slowly, on the 

 antisiphonal side, to a point a little in advance of the midlength, after 

 which it narrows somewhat more rapidly to the commencement of the 

 body chamber. On the siphonal side the margin of the septate portion 

 is shallowly concave posteriorly and slightly convex anteriorly. Body 

 chamber oblique, short, occupying about one-third the entire length, 

 contracted and obliquely truncated anteriorly. At its commencement 

 posteriorly the body charnber is broad and bounded by a rather deep, 

 obliquely transverse groove, which is almost parallel to the septa nearest 

 to it ; in front of this groove the chamber narrows rapidly, but at first 

 convexly, towards the aperture, behind which there is a broad and shal- 

 lowly concave constriction. Shape of the aperture not certainly known, 

 but it appears to have been simple, entire, subovate and rather narrow. 



Sutures nearly straight but slightly arched posteriorly ; oblique ante- 

 riorly, rather wide apart on the antisiphonal side, and faintly convex on 

 its median line, — much closer together on the siphonal side and slightly 

 concave on its median line: siphuncle inflated between the septa, nummu- 

 loidal, and placed very near to the margin of the straighter side. 



Surface markings unknown. 



