460 



Fossils of the Chazy Limestone. 



plane, — the apical half being gradually turned towards the flat 

 side, so as to constitute a sub-spiral curve. The width at the 

 base of the most perfect specimen collected is sixteen lines, thick- 

 ness nine lines ; length along the outer curve four inches, from 

 the apex in straight line to the inner angle at the base fifteen 

 lines, and to the outer angle two inches and three lines. On the 

 convex side the structure is seen to consist of successive .thin 

 laminae at right angles to the length, the unequal development of 

 which forms a sort of a squamose and transversely undulated 

 surface. This operculum resembles that of M. Peachii, but it lis 

 larger and more strongly curved. I have seen no perfect spe- 

 cimens. 



While the differences in the size of the whorls distinguished 

 this species from M. Peachii, its operculum shews at a glance 

 that it cannot be either M. Logani or M. Magna. 



I have seen no specimens with the shell preserved. In the cast of 

 the interior the inner whorls are quite ventricose, instead of flat, 

 in some of the individuals ; but in others, from the same locality, 

 nearly flat. 



Locality and Formation. — Mingan Islands. Chazy Limestone. 



Collectors — Sir W. E. Logan, J. Richardson. 



There are apparently two other species of Maclurea in the 

 Chazy, one of which may be M. Logani and the other M. Magna ; 

 but they require further examination . 



Cephalofoda (15 species). 

 Orthoceras Shumardi, N. s. 



Fig. 36. 



Fig. 36. — Longitudinal section of 0. Shumardi, shewing the distance 

 of septa and the position of siphuncle. 



Description. — Elongate, cylindrical, section circular, tapering 

 at the rate of a little more than half a line to the inch, septa rather 

 strongly convex, distant nearly half the diameter; siphuncle about 

 one fifth the whole diameter, and with its centre distant from the 



