288 ASS1NN1B0INE AND SASKATCHEWAN EXPEDITION. 



clrical with a broad, shallow constriction above and 

 below each of the narrow annulations which mark the 

 attachment of the septa. There are eight of those septal 

 rings at the following distances from each other, com- 

 mencing 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 and 7th, thir- 

 teen 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 from 

 the centre. My impression is, that this is a large ortho- 

 ceratite with distant septa and a nearly central siphuncle 

 since the annulations have a scarcely perceptible obli- 

 quity. 



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. 



Locality and formation.— Cat Head, Lake Winnipeg, 

 supposed to be Silurian. 



A small serpulite appears to be common at Punk 

 Island ; it much resembles the large species of the Chazy 

 limestone. 



The occurrence of M. parviuscula, II. umbilicata, the 



