THE TEENTON LIMESTONE OF MANITOBA. 81 



calcareous animal secretion, with the exception of a narrow cylindrical channel along the 

 centre. This central canal is cloarly indicated in the specimen and has a diameter of 

 nearly two lines. 



" Dedicated to Sir George Simpson, Grovernor of the Hudson's Bay Company." 



Since this description was published, a few specimens of siphuucles with very simi- 

 lar characters to those of O. Simpsoni, and which are therefore probably referable to that 

 species, have been collected at each of the following localities in or on Lake "Winnipeg. 

 Commissioners' (formerly called Cranberry) Island, seven miles east of Cat Head, D. B. 

 Bowling, 1890 ; Swampy Island, ten miles north-east of Cat Head, .1. B. Tyrrell, 1889, and 

 D. B. Bowling and L. M. Lambe, 1890 ; Black Island and Snake Island, Messrs. Bowling 

 and Lambe, 1890 ; and Bog's Head (two or three miles east of Snake Island) T. C. Weston, 

 1884, and L. M. Lambe, 1890. 



Some of the specimens from these localities are much longer and of course proportion- 

 ately thicker than the type from Cat Head, but the increase in thickness in all of them is 

 so slow as to be scarcely appreciable. In the type, the septal annulations certainly cross 

 the siphuucle at nearly right angles, as described by Mr. Billings and as represented in his 

 figure, a reproduction of which, in outline, is given on Plate VII, fig. 2, but in the 

 majority of specimens here referred to O. Simpsoni, which have been collected since, this is 

 bv no means always the case. Thus, in a specimen from Bog's Head, which is nearly two 

 feet long and a portion of which is represented in outline on Plate VII, fig. 3, the septal 

 riugs cross the siphuncle somewhat obliquely. 



The only specimen, presumably referable to this species, in which any remains of the 

 septa and outer shell are preserved, as well as the siphuucle, is the large fragment from 

 Swampy Island represented in outline by figure 1 of Plate VIII. This specimen, which 

 is about four inches in length and not quite three inches and a half in breadth, has been 

 worn down on one side in such a way as to give a natural and longitudinal section of the 

 shell, showing the edges of the septa and the lateral margins next to the test, as well as 

 the siphuncle. The latter is seen to be eccentric and sublateral but not quite marginal, 

 and to occupy, at its thickest part, rather more than one-third of the entire diameter. As 

 exposed in this section, the septa are seen to be rather deeply concave internally, but the 

 nature of the markings of the exterior of the test is still unknown. 



Orthoceras semiplanatum. (Sp. Nov.) 



Plate VIII, figs. 3 and 3a. 



Shell compressed subcylindrical, 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 shallow ly concave on the flattened side, slightly convex 

 on the other, and closely approximated, the six interior 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. 



Sec. IV, 1891. 11. 



