8U WHITEAVES ON THE OETHOCEEATID^ OF 



No. 2, is about eight inches iu length, by two inches and three and a half-tenths in its 

 maximum thickness at one end and not appreciably more at the other. Judging by its 

 thickness, No. 2 could very well have formed part of the anterior end of No. I, and both 

 are from the same locality. At the rate of taper of three-tenths of an inch per foot, it is 

 estimated that specimen No. 1 would have to be eight inches longer anteriorly than it 

 now is, before it could be as thick as No. 2. This would give thirty-five inches for No. 1, 

 eight for No. 2, and eight for the interval between them, or a total of four feet and a 

 quarter for the siphuncle only, which, even then, would be imperfect at both ends. 



In their proportionate thickness and probably submarginal position, as well as in the 

 irregularity and gradual expansion of their eudosiphons, these siphuncles seem to agree 

 better with those of Endoceias than with those of Orlhocerus proper. Although no clearly 

 defined sheath or sheaths have yet been detected ia them, they appear to be most nearly 

 related to that section of the genus Enduceras which Professor Hyatt has difierentiated 

 under the name Sannioniles, Waldheira, and iu this view of their affinities the writer's 

 opinion has recently been endorsed by Professor Hyatt. Specifically, they seem to differ 

 from the type of Ortlioceras Simpsoni, Billings (which may be an Endocerns) in their huge 

 size and proportionate thickness, but, more especially, in their more rapid increase in 

 thickness, though this increase is still so very gradual as to be not readily appreciable in 

 the comparatively short fragments that are usually obtained. 



Orthoceras SiMPSONi, Billings. 

 Plates VII, figs. 2, 2a and 3 and VIII, fig. 1. 



Orlhocrrag Simpfom, Billings. 1859. In Hind's Kep. Assinib. and Saskatfh. Expl. Exped., p. 186, pi. i, fig. 1. 



The type of this species, which is still preserved in the Museum of the Geological 

 Survey, was collected by Professor H. Youle Hind in 1858 at Cat Head, on the western 

 shore of Lake "Winnipeg and is thus described by the late E. Billings, " The specimen is 

 a portion of the siphuncle, nine inches aud one-fourth iu length, eleven lines at the larger 

 extremity, and ten at the smaller. It is nearly cylindrical, with a broad, shallow con- 

 striction above and below each of the narrow annulations which mark the attachment of 

 the septa. There are eight of these septal rings at the following distances from each 

 other, commencing at the smaller extremity. Between the 1st and 2nd, fourteen lines ; 

 2nd and 3rd, twelve lines ; 3rd and 4th, ten and a half lines ; 4th and 5th, thirteen and a 

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

 an"-les, but if the septa are concave then the annulations will be oblique if the siphuncle 

 be at all removed from 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 iu which the siphuncle became gradually filled with a solid 



