228 



This species is placed in the genus Discoceras s ilely on a count of the 

 doi'sal position of its siphuncle, and at the suggestion of Professor Hyatt, 

 who has seen one of the specimens. Externally it is very similar, 

 especially in the style of its surface markings, to the fossil from Lorette, 

 in the province of Quebec, which Mr. A. H. Foord described and figured 

 under the name Trochoceras Ralli on page 42, figs. 4, a-h, of the second 

 part of his Catalogue of the Fossil Cephalopoda of the British Museum, 

 but in specimens from several localities in that province, in the Museum 

 of the Survey, which are apparently referable to T. Ualli, the siphuncle 

 is placed on the venter. 



Trochoceras (?) McCharlesii, Whiteaves. 



Trochoceras McCharlesii, Whiteaves 1889. Trans. Royal Soo. Canada, vol. VII., 



sect. 4, p. 81, pi. 16. 



" Shell very large (the only specimen known to the writer, w,hich is 

 septate throughout, having a maximum diameter of ten inches and a-half) 

 and composed of about three apparently separatg but closely contiguous 

 volutions, which are circulnr in transverse section, and which increase 

 rather slowly in size : they are also slightly ^-symmetrical and enrolled 

 on very nearly but not quite the same plane, the spire being sunk a little 

 below the highest level of the outer whorl. 



" Surface of the outer volution marked by very numerous, close-set, 

 rounded and flexuous ribs, which are rather narrow but unequal in size, 

 with an average breadth of about three millimetres.'' Across the sides 

 the ribs curve obliquely and convexly backward and outward, and on 

 the periphery each rib makes a broad, shallowly concave and backwardly 

 directed sinus. 



On and near the periphery or venter, the only place where they 

 happen to be visible, the sutural lines run parallel with the ribs on the 

 test, though the former are placed much further apart, the average 

 distance between them being about nineteen millimetres. Position of 

 the siphuncle unknown. 



The specimen upon wl.ich this species was based was collected at East 

 Selkirk by Mr. A. McCharles in 1884. About one-third of this speci- 

 men has been broken off, but the part remaining presents a very 

 instructive transverse section of the shell at a right angle to the direction 

 of the volutions. A considerable portion of the test is well preserved on 

 the outer volution, and in those places where the test has been accidentally 

 removed, the characters of the septa are well shown. The two inner 

 whorls are not nearly so well preserved as the outer volution, and the 

 asymmetry and separation of all three are best exhibited in the transverse 

 section afforded by the specimen. 



