296 
AUG. F. FOEESTE 
23. Actinoceras tenuifilum ursinum Var. nov. 
Plate XXVIII, fig. 3; Plate XXXII, fig. 6 
Actinoceras Bigsbyi (-A. tenuifilum ?) Holtedahl, Paleozoic 
Series of Bear Island, 1919, p. 131, pi. 13, fig. 5. 
Apical angle 16 degrees. Siphuncle apparently nearly central, 
its diameter varying from 65 per cent of that of the conch at 
the base of the specimen to 57 per cent at its top. From 9 to 
9.5 camerae occupy a length equal to the diameter of the conch 
at the top of the series being counted. The structure of the 
annular segments of the siphuncle and the degree of concavity 
of the septa closely resembles that of Actinoceras tenuifilum 
centrale, from the Black River limestone of Watertown, New 
York. The chief differences consist in the relatively greater 
number of camerae and in the greater apical angle of the conch. 
Locality and Horizon. — From the western part of the Antarc- 
tic Mountain area on Bear Island. In the Tetradium limestone 
member of the Heclahook System, regarded as of Black River 
age. Original of figure 5 on plate 13 in the publication cited 
above. In the Palaeontologisk Museum, Kristiania, Norway. 
Collected by Floltedahl in August, 1918. 
Remarks. — The species later named Actinoceras Bigsbyi by 
Bronn was first figured and described by Bigsby from the equiva- 
lent of the Black River limestone on Thessalon Island in the 
northwestern corner of Lake Huron. Bronn’ s first figure (Leth. 
Geog., 1, 1837, p. 98, Plate I, fig. 8) is a reproduction of Bigsby’s 
figure 1 on plate 25 of the Trans. Geol. Soc. London, 1, 1824, 
p. 198, in which, according to Foord, the segments of the siphun- 
cle are not oblique to the long axis of the siphuncle (Foord, 
Catalogue of Fossil Cephalopoda, 1888, p. 170). Bronn’s 
second figure, published on his plate 1', is that of a species 
having oblique segments of the siphuncle, the latter being in 
contact with the ventral wall of the conch. Since Bronn’s first 
figure must be regarded as the type, it would be desirable to 
know how closely it resembles the form here described as Actino^ 
ceras tenuifilum centrale. As far as can be judged from the figure 
presented by Bigsby, Actinoceras bigsbyi has an apical angle of 
