217 



"The genus Foterioceras was thus originally defined by M'Coy: — 'Shell 

 fusiform, short ; mouth contracted ; siphuncle dilated between the cham- 

 bers, eccentric. Distinguished from the true Orthoceratites by its short 

 fusiform contour, and contracted mouth.' This diagnosis is accompanied 

 by a small diagram, which shews that, although the body chamber nar- 

 rows rapidly from its commencement up to the aperture, yet the aperture 

 itself is simple and entire, and neither T-shaped or lobate as in Gompho- 

 ceras, nor contracted in the middle and expanded at both ends as in 

 Phragrnooeras. 



"The validity of the genius Foterioceras is not recognized by Barrande, 

 Fischer, Zittol and others, who place the name among the synonyms of 

 Gomphoceras. On the other hand, in the first part of his Monograph of the 

 British Fossil Cephalopoda," Professor J. F. Blake " accords full generic 

 rank to Foterioceras on the ground that ' the only species described by 

 M'Coy, as well as his diagram, indicates a genus with the form of a 

 (TOHipAoceras without its peculiar aperture.' In the same volume. Professor 

 Blake contends that Oncoceras, Hall, is synonymous with Foterioceras, 

 and states that Professor Hall's "actual type, as well as others which have 

 been referred to the genus, in no respects differ from M'Coy's genus. 

 To this contention the present writer feels compelled to demur, as the 

 statement by which it is supported seems to be at variance with the 

 known facts of the case. If the genus Foterioceras is to be retained at 

 3.\[, in the sense in which it was defined by M'Coy, the name will pro- 

 bably have to be restricted to those straight Gom^jhoceras-like shells in 

 which the aperture is simple and entire, and it is in accordance with this 

 definition of its character that the name will be used in the present 

 paper. In Oncoceras, on the other hand, the shell is always distinctly 

 curved and inflated in a peculiar manner in advance of the midlength, 

 while its body chamber is transversely constricted just behind the aper- 

 ture. According to Professor Hall the aperture of Oncoceras is constricted, 

 but as Mr. E. Billings asserts that it is oval,* the constriction referred 

 to by Hall may have been meant to refer to that immediately behind 

 the aperture." 



In the outline drawing of the type of the species on Plate 14 of the 

 seventh volume of Transactions of the Royal Society of Canada, although 

 the contour and exact dimensions of the original are correctly represented, 

 the sutural lines are slightly restored and the supposed outline of the 

 aperture, on one side of the specimen, is indicated by a dotted line. 



POTEKIOCEKAS APERTUM, Whiteaves. 



Poterioeeras apertum, Whiteaves 1889. Trans. Royal Soe. Canada, vol. VII., 



sect. 4, p. 78, pi. 14, figs. 2-4; and (1891) 

 ibid., vol. IX., p. 87, pi. 11, fi§s. 2 and 3. 



Geological Snrvey of Canada, Rep. Progr. 1853-56, p. 311. 



