ENDOCERATID^. 
157 
species. The dimensions of the specimen are : — length 2 inches, 
greatest breadth 2 inches, least IJ inch. There are about ten in- 
vaginated sheaths, succeeding each other with great regularity, and 
var}'ing from 1 to 2 lines apart. Xo traces of the septa can be seen. 
Horizon. Calciferous Sandstone ( = Tremadoc). 
Locality. Mingan Island, Gulf of St. Lawi’ence (?). 
Genus PILOCERAS, Salter h 
Gen. Char. Shell more or less broadly conical ; slightly curved ; 
somewhat compressed laterally ; elliptical in section. Siphuncle 
marginal ; formed, as in Endoceras, by the prolongation and con- 
junction of the necks of the septa ; very large ; partaking of the 
curvature of the shell ; provided internally with one or more conical 
or funnel-shaped sheaths, which are united at the top with its 
margin. These sheaths apparently communicated with one another 
by means of the endosiphon which passed from the initial chamber 
into the siphuncular cavity by means of a large foramen (fig. 17, 
II. a), situated on the inner curvature of the siphuncle a little above 
the apical point 
The history of this genus is an interesting one. 
It was founded by Salter upon the siphuncle of a shell closely allied 
to Endoceras. Salter supposed that the invaginated sheaths obseiwed 
in the siphuncle of Piloceras “ represented the siphuncle and septa 
combined,” the septate part of the shell not being preserved in the 
specimens described by him. 
A year after the appearance of Salter’s memoir, E. Billings (at that 
time Palaeontologist to the Canadian Geological Survey) described a 
fossil from the Calciferous Sandstone ( = Tremadoc) under the name 
of Piloceras Canadense This exhibited the septate part of the shell 
in conjunction with the siphuncle. 
The general form of this species was well characterized by Billings 
as that of a “ short, thick, curved Orthoceratite.” 
This appears to have been the first discovery of the septa of 
Piloceras, associated with its siphuncle ; for the generic identity of 
Salter’s and Billings’s species is now put beyond aU doubt. 
^ Quart. Joum. Geol. Soc. vol. xxv. 1859, p. 376. 
* Hyatt in his definition of Piloceras {loc. cit. p. 266) states that it is “ often 
annulated ; ” but this is evidently an inadvertence, because the outer shell was 
unknown when he wrote, and remained so until the specimens described by Prof. 
Whitfield saw the light, and these showed only “ a few transverse wrinkles of 
growth.” He probably had in his mind the detached siphuncles, which have an 
annulated appearance caused by the adherent remains of the septa. 
3 Canadian ISlaturalist and Geologist, vol. v. p. 171. 
