290 
AUG. F. FOEESTE 
ohliqua Stokes; in the type of Huronia septata Parks this number 
is exactly 2. The chief difference between Huronia septata and 
Huronia ohliqua noted so far consists in the distinct obliquity 
of the upper surface of the segments of the siphuncle in the latter 
and in the almost directly transverse slope of this surface in the 
former species; thus indicating that the siphuncle of Huronia 
ohliqua is strongly excentric in position while that of Huronia 
septata is nearly central. In this respect Actinoceras amundseni 
resembles Huronia ohliqua more closely. However, in Actino- 
cerds amundseni the tendency toward a concave lateral outline 
along the lower half of 'the segments of the siphuncle is much 
less conspicuous, and this difference is regarded as sufficient to 
indicate a new species. The rather angular downward deflection 
of the sutures of the septa along the median line of the ventral 
side of the conch may be another distinctive feature, although 
it is shared with Actinoceras imhricatum Hisinger, and I suspect 
that it is present also in other species in which the siphuncle is 
virtually in contact with the ventral wall of the conch. 
To me the general aspect of Actinoceras amundseni and of 
Huronia septata is Silurian rather than Ordovician, but lithologi- 
cally the type of Actinoceras amundseni resembles other speci- 
mens from the Boothia Felix-King William Land area regarded 
as of Black River age, and the type of Huronia septata was 
obtained at the Lower Rapids of the Shamattawa River, where 
the general assemblage of fossils is Ordovician. 
The type of the genus Huronia is Huronia higshyi Stokes. 
In this species the segments of the siphuncle resemble short 
inverted pestles, the lower two-thirds of each segment being 
nearly cylindrical, the upper third enlarging more or less ab- 
ruptly. Huronia vertehralis Stokes and Huronia minuens Bar- 
rande have the same types of structure. In Huronia ohliqua 
Stokes, Huronia turhinata Stokes, and Huronia distincta Barrande 
the lower part of the segments of the siphuncle is turbinate 
rather than cylindrical. The figure of Huronia portlocki Stokes 
resembles that of an Actinoceras in which the septa are adnate 
to the lower face of the annular segments of the siphuncle. 
Orthoceras persiphonatum Billings also appears to be an Actino- 
