1898] Whiteaves — On some Fossil Cephalopoda. 123 



ceras biangulatum, Hyatt, The fifth specimen, which was collected 

 at Table Head by Mr. Richardson in 1861, is a small specimen 

 of Lttiiites Pluto, Billings, but clearly not the type of that 

 species. 



B. — From the Silurian ( Upper Silurian) rocks of 



Manitoba. 



Tripleuroceras Robsonl (Sp. nov.) 



Shell large, robust, longicone, straight and increasing very 

 slowly in breadth and thickness, flattened in the broad siphonal 

 and presumably ventral legion, but rounded and much narrower 

 at the sides : characters of the antisiphonal side and nature of 

 the surface markings unknown. Sutures of the septa broadly 

 and concavely arched on the venter, nearly straight where they 

 pass over the sides ; the three or four next to the body chamber 

 closer together than those which immediately precede them. 

 Siphuncle marginal, presumably ventral, large, expanded between 

 the septa and apparently nummuloidal. 



Three imperfect and badly preserved casts of the interior of 

 shells of this species, from Stonewall, Manitoba, were presented 

 to the Museum of the Survey in the fall of 1897, two by Mr. 

 VV. H. Kobson, of Lethbridge, Alberta, and one by Mr. Donald 

 Gunn of Stonewall. The whole of the antisiphonal and presu- 

 mably dorsal region of each of these specimens is buried in a very 

 hard dolomitic limestone, so that it is doubtful whether they are 

 referable to Hyatt's genus Tripleuroceras or not. The two 

 presented by Mr. Robson are septate throughout, and the larger 

 one has a nearly cylindrical, septate but possibly adventitious 

 object, like a cast of the interior of the shell of a small Orthoceras, 

 some two inches in length and fully half an inch in thickness, 

 exposed in the middle of its siphuncle posteriorly. The one 

 presented by Mr. Gunn has a considerable portion of the ventral 

 side of the body chamber preserved, but the lateral margin on 

 both sides is very imperfect. 



The species seems lo differ from the " Orthoceras (Actino- 



