AKCTIC ORDOVICIAN AND SILURIAN CEPHALOPODS 
291 
ceras. An examination of the types will be necessary to deter- 
mine the relationship of these so-called Huroniae. 
In typical Huronia, the septa are adnate to the lower part 
of the successive segments of the siphuncle, from the base of 
the cylindrical part of each segment up to the outer margin of 
the lower face of the annular enlargement at its top. Huronia^ 
therefore, differs from Actinoceras only in the cylindrical elonga- 
tion of that part of each segment of the siphuncle which lies 
beneath the annulation. 
19. Actinoceras Sp. 
Plate XXVII, fig, 7; Plate XXXII, fig. 2 
Actinoceras sp. Holtedahl. On Some Ordovician Fossils from 
Boothia Felix and King William Land collected during the 
Expedition of the Gjoa. Videnskapsselskapets Skrifter, I, Mat- 
naturv. Klasse, 1912, No. 9, pi. Ill, fig. 2. 
Figured specimen. — The specimen consists of the ventral side 
of a phragmacone. Owing to weathering, the siphuncle and 
the adjacent parts of the septa are exposed. Near the base of 
the specimen the segments of the siphuncle have a maximum 
diameter of 20 mm.; the same diameter is shown 100 mm. 
farther up, at the top of the specimen. The diameter of the 
conch at the upper end of the specimen is estimated at 60 to 
65 mm. If this be correct then the diameter of the siphuncle 
is about one-third of tliat of the conch. The apical angle of 
the specimen is supposed to have been relatively small, possibly 
5 degrees, but the evidence for such an apical angle is not satis- 
factory. The location of the siphuncle is strongly excentric. 
This is indicated by the slope of its segments, the latter forming 
an angle of about 60 degrees with the vertical axis of the siphun- 
cle. In fact, the siphuncle probably was almost in contact with 
the ventral wall of the conch. 
About 9 camerae occupy a length equal to the estimated 
diameter of the conch. Nothing is known about the exact direc- 
tion of the sutures of the septa, but in other species with marginal 
siphuncles these sutures usually curve more or less strongly 
