IQI5] . PaLAEOzoIc FossILs FROM HupDSON Bay. 25 
ACTINOCERAS cf. BIGSBYI, Bronn. 
Plate VI, Figure 6. 
One broken fragment showing only the siphuncle and the inner 
parts of the septa. Septa somewhat variably spaced but averaging 
9g mm. apart. Siphuncle about 22 mm. in diameter evenly expanded 
in the posterior part of the interseptal space. The septa in contact 
with the posterior aspect of the rings, but separated from the anterior 
aspect by inwardly curved septal necks. In vertical section the outer, 
anterior wall of the nummuloidal expansion is broken in each segment, 
suggesting a communication between the interior of the siphuncle and 
the camerz. No endosiphonal structures preserved. 
This specimen, in all probability, is to be referred to A. bigsbyt: it 
closely resembles some of Barrande’s figures of that species, but is dis- 
tinctly different from the other specimen which I have referred to 
A. bigsby1 (Page 23), in that the septal necks, before expansion, are 
much shorter and pass less abruptly into the nummuloidal rings. The 
spacing of the septa and the size and shape of the siphuncle are almost 
exactly the same as in the figure given by Foord (Cat. Foss. Ceph., 
Brit. Mus: ps E04, Fig. 21): 
If the characteristic radial tubuli could be seen in the present example, 
there could be no hesitation in ascribing it to A. bigsbyi, and were it 
not for the distinct evidence of cylindrical structure in the anterior 
part of the siphuncular rings shown in Bigsby’s original figures, I should 
consider this specimen nearer to A. bigsbyi than the one described on 
page 23. 
Locality—Lower rapids, Shamattawa river, Manitoba. 
Horizon—Ordovician. 
No. 315 S. Royal Ontario Museum of Palaeontology. 
ACTINOCERAS RICHARDSONI MAGNUM, Parks, var. 
Cf. ACTINOCERAS RICHARDSONI, Stokes. 
Plate II, Figure 1. 
ACTINOCERAS RICHARDSONI, Stokes. Trans. Geol. Soc., ser. 2, Vol. V, pt. 3, p. 708, pl. 
LIX, figs. 2 and 3, 1840. 
CONOTUBULARIA CUVIERI, Troost. Mem. Soc. Geol. de France, tom. III, Ime. partie, 
p. 88, pl. 9, fig. 1, 1838. 
ORTHOCERAS (ACTINOCERAS) RICHARDSONI, Barrande. Syst. Sil. de la Bohéme, Vol. II, 
Texte III, p. 734, pl. CCX XXIV, figs. 2 and 3, 1847. 
ACTINOCERAS RICHARDSONI, Foord. Cat. Foss. Ceph., Brit. Mus., p. 172, 1888. 
ACTINOCERAS RICHARDSONI, Whiteaves. Trans. Royal Soc. Can., Vol. IX, sec. IV, p. 83, 
pl. IX, figs. 1, 2 and 2a, 1891. 
ACTINOCERAS RICHARDSONI MAGNUM, Parks. Bur. Mines of Ont., 22nd Rep., p. 191, 1913. 
