221 



Approximate dimensions of the most perfect specimen known to the 

 writer, which is imperfect at the posterior end: 180 millimetres, or a 

 little more than seven inches ; maximum breadth, from the siphonal to 

 the antisiphonal side, 106 mm. 



This specimen, which is figured in the seventh volume of Transactions 

 of the Royal Society of Canada, is a cast of the interior of the shell,, 

 collected by Mr. W. Chesterton at East Selkirk and presented to the 

 Museum of the Survey in 1888 by the Historical and Scientific Society 

 of Manitoba. A larger but less pecfect specimen in the Museum of the 

 Survey was collected at East Selkirk in 1884 by Mr. T. C. Weston. 



Oncooeras (magnum? var.) intermedium. 



Fig. 13. Oncoceras {magnura ? var. ) intermedium. Outline of a longitudinal section: 

 of the only specimen known to the writer, one-half the natural size. 



