82 WHITE AVES ON THE OETHOCERATID.^ OF 



Lower Fort Garry, Dr. R. Bell, 1880 : an imperfect and not very well preserved cast 

 of the interior of the shell, not quite three inches and a half in length, and showing two 

 inches and four-tenths of the body chamber, with about an inch of the septate portion. 

 The species resembles the O. pfanoconvexum of Hall, from the Trenton limestone of Wis- 

 consin, in its planoconvex transverse section and in the close approximation of its septa, 

 but differs therefrom in its much less rapid increase in thickness, less compressed sides, 

 and, more particularly, in the entirely different position of its siphuncle, which latter, in 

 O. planoconvexum, is said to be " centrally situated on the flattened side." 



Oethoceras Selkirkense. (Sp. Nov.) 



Plate VIII, figs. 2, 2a and 2b. 



Shell very nearly cylindrical, but increasing in thickness at the rate of about one 

 millimetre in two inches, slightly compressed in the dorso-ventral region, the outline of 

 its transverse section being rounded elliptical, with the larger diameter about one-fourth 

 larger than the smaller. Surface marked with narrow but very prominent distant annu- 

 lations, or transverse raised ridges, separated by flat intervals, which are about half as 

 broad as the maximum diameter of the tube, and transversely costulate where the test is 

 well preserved. Septa remote, each of the larger annulations of the test marking the 

 commencement of a new septum, and shallowly concave internally, as seen in longitudinal 

 sections through the centre of the tube ; siphuncle rather large, placed near the margin of 

 one of the flattened sides, and slightly contracted at the septa. Chamber of habitation 

 unknown. 



The largest specimen collected is not quite five inches in length. At a distance of a 

 little more than half an inch from its smaller extremity its maximum diameter is twenty- 

 five millimetres, and at about a quarter of an inch from its larger end the greatest thick- 

 ness is twenty-seven millimetres. 



East Selkirk, Manitoba ; two specimens, both collected in 1884, one by Mr. T. C. 

 Weston and the other by A. McCharles. 



Orthoceras Winnipegense. (Sp. Nov.) 



Plate VIII, figs. 4, 4a and 4b. 



Shell narrowly elongated, somewhat fusiform, very slightly inflated in advance of 

 the midlength ; outline of transverse section nearly rounded but approaching to elliptical. 

 Septate portion cylindro-conical, and increasing very slowly in thickness ; chamber of 

 habitation broadly but shallowly constricted in the middle, and a little narrower at the 

 aperture than at its commencement. Surface markings unknown, though the interior of 

 the test is marked by closely disposed and exceedingly minute, transverse raised lines. 

 Septa, as shown in the longitudinal section represented by fig. 4b, seven millimetres and a 

 half apart at the smaller end, and eight mm. at the larger, as measured at their broadest 

 part, next to the siphuncle ; siphuncle slightly eccentric, narrow, almost cylindrical, but 

 faintly constricted at the septa. 



