208 



The very large submarginal and nummuloidal siphuncle varies in its 

 proportionate size in different specimens, though its maximum diameter 

 is usually more than half that of the shell. It is very strongly inflated 

 between the septa, and both acutely and narrowly constricted at the 

 places where they join it. In the longitudinal section of a specimen 

 of this species represented by fig. 2 of Plate 9 of the volume referred 

 to, the posterior segment of the siphuncle is thirty -six. millimetres in 

 maximum breadth and nine in height, while the last perfect segment 

 anteriorly is forty-seven mm. in its greatest breadth by ten in height. 

 The endosiphon and the lateral tubuli which proceed from it are all well 

 shown in this and in similar sections. 



Figures 3 and Six on Plate 9 of the volume cited represent the apical 

 extremity of what appears to be an abnormally flattened specimen of this 

 species, in which the outline of a transverse section at the larger end (fig. 

 3a) is elliptical and not circular. 



AcTiNOCERAS BiGSBYi 1 Bronn. 



Orihocerce Bigsby 1824. Trans. Geol. Soc. Lond., ser. 2, vol. I., 



p. 198, pi. 25, figs. 1 and 2 (but not 3). 

 Actinoceras Bigshyi, Bronn 1837. Lethfea Geogn., Bd. I., p. 98, taf. 1, 



f. 8 (after Bigsby). 

 M M Stokes 1840. Trans. Geol. Soo. Lond., ser. 2, vol. 



v., pt. 3, p. 707. 



Actinoceras Lt/oni, Stokes 1840. Ih., p. 707, pi. 59, fig. 1. 



II .1 Castelnau 1843. Syst. Silur. de I'Amer. Septentr., p. 



32, p}. 17, figs. 1, a-h. 

 Ormoceras tenuifilum, Hall 1847. Pal. N. York, vol. I., p. 55, pis. 15, 



16, and 17, figs. 1, a-h. Teste E. Billings, 



in Geol. Canada, 1863. 

 Ormoceras Lyonii, Hector 1861. Quart. Jour. Geol. Soc. Lond., vol 



XVII., p. 439 (Salter's determination). 

 Orthoceras Bigsbii, Billings 1863. Geol. Canada, p. 149, figs. 109, a-b, 



and Appendix, p. 949. 

 Orthoceras {Actinoceras) Bigsbyi,'Barra,nde.. .ISTi. Syst. Silur. de la Boheme, vol. I., 



Texte 3, p. 7.34, and pi. 231, figs. 4 and 5 



(copied from Dr. Bigsby) and pi. 437, figs. 



10-16. 

 Orthoceras {Ormoceras) tenuifilum, Barrande.1874. lb., p. 754, pi. 237, figs. 5-7. 



Actinoceras Bigsbyi, Foord 1888. Cat. Ceph. Brit. Mus., p. 168. 



II M Whiteaves 1891. Trans. Royal Soo. Canada, vol. IX., 



sec. 4, p. 84, pi. 10, fig. 2. 



One of the species of fossils collected by Sir James Hector in 1857 at 

 Lower Fort Garry was identified by the late Mr. Salter with Ormoceras 

 Lyonii, which Mr. Foord includes among the synonyms of Actinoceras 

 Bigsbyi, Bronn. Specimens, which the writer has referred to A. Bigsbyi, 

 have since been collected in the Red River valley, at East Selkirk, by 

 A. McCharles in 1884; and on or around Lake Winnipeg, at Little 



