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half lines ; 5th and 6th, fifteen lines ; 6th and 7th, thirteen and a half 

 lines ; 7th and 8th, twelve and a half lines. The annulations are nearly 

 at right angles to the length, and we must infer from this fact either that 

 the septa are scarcely at all concave, or that the siphuncle must be central 

 or very nearly so. If in an orthoceratite the septa are flat, then, no 

 matter whether the siphuncle be central or not, the septal annulations 

 must be at right angles, but if the septa are concave then the annulations 

 will be oblique if the siphuncle be at all removed fi'om the centre. My 

 impression is, that this is a large orthoceratite with distant septa and a 

 nearly central siphuncle, since the annulations have a scarcely perceptible 

 obliquity. 



"It is one of those species in which the siphuncle became gradually 

 filled with a solid calcareous animal secretion, with the exception of a 

 narrow cylindrical channel along the centre. This central canal is clearly 

 indicated in the specimen and has a diameter of nearly two lines. 



'' Dedicated to Sir George Simpson, Governor of the Hudson's Bay 

 Company." 



Since this description was published, a few specimens of siphuncles 

 with very similar characters to those of 0. Simpsoni, and which are 

 therefore probably referable to that species, have been collected at each 

 of the following localities in or on Lake Winnipeg : Dog Head, T. C. 

 Weston, 1884, and L. M. Lambe, 1890; Little Black Island, J. B. Tyrrell, 

 1889, and D. B. Dowling and L. M. Lambe, 1890; Snake Island, Messrs. 

 Dowling and Lambe, 1890; and Commissioners Island, D. B. Dowling, 

 1890. 



Some of the specimens from these localities are much longer and of 

 course proportionately 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 siphuncle 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 7, fig. 2, of the 

 ninth volume of Transactions of the Royal Society of Canada, but in the 

 majority of specimens there referred to 0. Simpsoni, which have been 

 collected since, this is by no means always the case. Thus, in a specimen 

 from Dog Head, which is nearly two feet long and a portion of which is 

 represented in outline on Plate 7, fig. 3, of the volume just referred to, 

 the septal rings 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 siphuncle, 

 is the large fragment from Little Black Island, represented in outline by 

 fig. 1 of Plate 8 of the volume cited. 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 



