Fossils of the Chazy Limestone, 463 



Orthoceras Minganense (Billings.) 



(0. Minganense, Report G. S. C, 1856, page 319.) 



Occurs in both Chazy and Black River limestones at the Min- 

 gan Islands. 



Orthoceras Allumettense (Billings). 



(0. Allumettense, Report G. S. C.j 1856, page 331.) 



Description. — Section nearly circular, tapering at the rate of 

 one line and a half to the inch ; siphuncle moniliform eccentric, its 

 centre distant from the centre of the shell half its own diameter; 

 septa convex, from two to two lines and a half distant ; surface 

 apparently smooth. 



In a specimen three inches long, thirteen lines in diameter at 

 the larger and eight and a half lines at the smaller extremitv, the 

 dilations of the siphuncle are four lines wide, and the distance of 

 the septa gradually diminishes from two and a half to two lines. 

 On its passage through the septa the siphuncle is constricted to 

 the diameter of one line, and the segments or expansions between 

 the septa are discoid, with rounded edges, each being a sphere 

 compressed at opposite sides. The inner margins of the segments 

 of the siphuncle are in contact with a line drawn longitudinally 

 through the centres of the septa. The outer margin is distant 

 from the centres of the septa the whole diameter of the siphuncle. 

 The segments of the siphuncle are not disposed at right angles to 

 the length of the shell, but obliquely, sloping from the outside 

 inwards and towards the apex or smaller extremity. 



Locality and Formation. — Chazy sandstone at Aylmer and 

 township of Clarence; Black River limestone, Pauquette's rapids. 



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



Orthoceras Antenor, N. s. 



Description. — The only specimen of this species that I have 

 seen is eight inches in length, and tapers from fourteen lines at 

 the larger to four and a half lines at the smaller. The two septa 

 visible at the larger extremity are distant two lines and two thirds. 

 The surface is beautifully cancellated by fine but distinct longitu- 

 dinal lines, about twelve to one line, crossed at right angles by 

 much finer but still distinct encircling striae. The shell is curved 

 so as to form an arch, of w T hich the base is eight inches and the 

 height in the middle eight lines. 



