2U 



transverse section nearly lenticular, though the venter is a little flatter 

 than the dorsum. Surface markings unknown. Septa rather closely 

 approximated, their sutures averaging from ten to eleven millimetres 

 apart on the median line of the dorsum, each suture being broadly concave 

 on the dorsum and venter, and produced into a large obtusely pointed 

 saddle on each of the lateral angles. Siphuncle ventral, marginal, 

 strongly inflated between the septa, but very small proportionately, its 

 thickest portion occupying not much more than one-seventh the maximum 

 diameter of the tube. The constrictions between the siphonal inflations 

 are very deep, and, when viewed in longitudinal section, appear as 

 narrow incisions which cut obliquely backward and inward, on each side, 

 thus giving a very peculiar appearance to the siphuncle. 



"Approximate dimensions of the specimen described : length rather 

 more than ten inches ; maximum diameter, at the smaller end, five 

 inches, the corresponding diameter at the larger end being six inches and 

 a half." 



East Selkirk, L. M. Lambe, 1890; a single specimen of the septate 

 portion of the shell. Wekusko Lake, District of Saskatchewan, J. B. 

 Tyri'ell, 1896, a specimen which is also septate throughout, imperfect at 

 both ends, and which measures about a foot in length, by seven inches 

 and three-quarters at the larger end. Two specimens from the Galena 

 limestone of Minnesota have recently been identified with this species by 

 Dr. John M. Clarke. 



Teipterocekas semiplanatum, Whiteaves. (Sp.) 



Orthoceras semiplmuitum, Whiteaves 1891. Trans. Royal Soo. Canada, vol. IX., 



sect. 4, p. 81, pi. 8, figs. 3 and 3«. 



Shell compressed subcylindrioal, increasing very slowly in thickness (at 

 the rate, so far as can be ascertained, of three millimetres and a half in a 

 length of five centimetres), nearly planoconvex in transverse section, one 

 side being broadly and very gently convex and the other nearly flat, the 

 shorter of the two diameters of the tube being about one-third less than 

 the longer, and the lateral margins narrowly rounded. Surface markings 

 unknown ; sutures of the septa shallowly concave on the flattened side, 

 slightly convex on the other and closely approximated, the seven anterior 

 chambers together measuring half an inch, on the median line of the 

 flattened side ; siphuncle small, cylindrical, placed close to the margin of 

 the convex side. 



"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 



