154 
NAUTILOIDEA. 
Eew, if any, will adhere now to the view originally expressed 
by Professor Hall (loc. cit. p. 208), that the siphnncular sheaths in 
Endoceras performed embryonic functions, and that they contained 
within themselves the young shells. But it was upon this 
hypothesis that Prof. Hall rested his conclusions as to the affinities 
of the forms in question. Judging from his figures I can see no 
necessary connection between Endoceras ^roteiforme and its so- 
called varieties. The siphuncle is figured in two instances, viz. 
pi. xlv. f. 4 6 (^E. proteiforme, var. lineolatum) and pi. xlvi. f. 4 & 
{E. proteiforme, var. strangulatum), but neither in size nor position 
does it resemble the siphuncle of an Endoceras. I am therefore 
strongly inclined to the opinion that these forms really belong to 
the genus Orthoceras ; but in the absence of more abundant material 
to work upon, I cannot at present say anything positive upon this 
point. 
It may be added that Prof. H. A. Nicholson, in his Eeport upon 
the Palaeontology of Ontario (Toronto, 1875), p, 39, records the 
occurrence in the Utica shales of Whitley and Collingwood [Canada 
West] of “ a species of Orthoceras which may be provisionally 
referred to Endoceras proteiforme of Hall, var. taniistriatum.'^ 
Prof. Nicholson remarks that these specimens, though resembling 
the genus Theca in their pointed triangular form, possess distinct 
septa, which are placed about one and a half lines apart, though 
these, he adds, are not always recognizable. 
Horizon. Trenton Pormation (= Bala Limestone Group). 
Localities. Trenton Falls, New York State; Montreal. 
Bepresented by a few fairly good specimens, those from Montreal 
presented by I)r. J. J. Bigsby, F.E.S.] 
Endoceras magniventrum, Hall. 
1847. Endoceras magniventrum, Hall, Pal. of New York, vol, i. p. 218, 
pi. liii. If. 1 a-e. 
Sp. Char. “ Elongated, very gradually tapering ; siphuncle 
very large, occupying about three fifths the diameter of the 
shell ; septa extremely convex, distant one eighth the diameter of 
the shell. The specimen figured is a fragment of an individual, 
which, when perfect, could not have been less than six feet in 
length. The septa are more convex than in any other species known 
to me. . . . The siphuncle is proportionally larger, and the 
septa more approximate than in any other species described.” 
(HcdJ.) 
Remarks. A large fragment of this species is contained in the 
