292 
AUG. F. FOERSTE 
downward on the ventral side of the conch. Where the diame- 
ter of the conch is 60 mm. the depth of concavity of the septa 
equals at least 16 mm. The segments of the siphuncle are 
strongly nummuloidal, contracting from a maximum diameter 
of 19 mm. to one of 14 mm at the low^er margin of the septal 
necks. The latter are short, less than 1 mm. in length, the 
distance between successive segments of the siphuncle equalling 
scarcely 1 mm. 
The central part of the siphuncle is occupied by a thick strand 
of calcareous deposits enlarging toward the top ; from this central 
strand deposits radiate toward the upper part of the segments 
of the siphuncle. The strand itself consists of radiating elements 
2 or 3 mm. wide, transversely concave when viewed from be- 
neath, sometimes weathering so as to present an appearance 
slightly like that of a Cystiphyllum. 
Locality and Horizon. — From some unknown locality, prob- 
ably of Black River age, either on Boothia Felix or on King 
William Land. In the Palaeontologisk Museum, Kristiania, 
Norway. Collected by Lieut. Godfred Hansen in 1903-04. 
Remarks. — In the structure of its siphuncle this species resem- . 
bles Actinoceras tenuifilum from the Black River limestone at 
Watertown, New York. It differs in having relatively more 
numerous camerae and the size of the siphuncle appears to be 
relatively much smaller. It probably is a new species but not 
sufficiently well preserved to serve as a^type. 
20. Actinoceras Sp. 
Plate XXIX, fig. 2 
The specimen consists of a vertical dorso-ventral section of 
the phragmacone formed during the breakage of the rock. This 
section exposes the walls of the conch, the septa, and the hollow 
spaces formerly occupied by the nummuloidal segments of the 
siphuncle. 
The apical angle of the specimen in a dorso-ventral direction 
is 9 degrees. The number of camerae in a length equal to the 
dorso-ventral diameter of the conch varies from 3 at the base 
