22 TRANSACTIONS OF THE ROYAL CANADIAN INSTITUTE. [VOL. XI 
The much greater slant of the outer side of the whorl and the more 
acute peripheral angle separates this form from M. subovata; the large 
umbilicus distinguishes it from M. logani. The sharply angulated 
periphery and the flattening of the outer side of the volutions on the 
convex side separate it from M. bigsbyt. 
This form may possibly be identical with the Maclurea described by 
Whiteaves from the Nelson river (See page 20). 
Locality—Lower rapids, Shamattawa river, Manitoba. 
Horizon—Ordovician. 
No. 350 S. Royal Ontario Museum of Palaeontology. 
CEPHALOPODA 
ORTHOCERAS (THORACOCERAS) LEPIDODENDROIDES, Parks. 
Plate II, Figure 4. 
ORTHOCERAS LEPIDODENDROIDES, Parks. Bur. Mines of Ont., 22nd Rep., pt. I, p. 190, 
1913. 
The species is founded on a single cast of a portion of a longicone. 
The specimen is 75 mm. long and shows portions of 8 camerae: it has 
been badly crushed and now measures 60 mm. by 30 mm. If round its 
diameter would be 45 mm. The outline was probably ovate with a 
greater diameter in one direction. The septa are somewhat irregularly 
spaced, but the interval would average about 6 mm. In the crushed 
form the specimen shows evidence of flexuous sutures with low lobes 
and saddles, but this appearance may be entirely due to deformation. 
The one remarkable and characteristic feature is that the whole 
surface of the cast is raised into blunt nodes arranged in a diagonal 
manner around the cone. These nodes are 4 to 6 mm. apart and besides 
the diagonal arrangement they are disposed in rows on each camera. 
While this latter statement is generally true, there is evidence in certain 
parts of the specimen that the nodes are independent of the camere. 
The drawing is much restored, as the ornamentation has been destroyed 
by weathering in certain parts: the nodes have been restored with rather 
too great regularity with respect to the camere. The nodes are blunt, 
from 4 to 5 mm. long, and wider anteriorly. 
The genus Orthoceras, as now defined, is confined to forms with a 
smooth shell: it would appear that the present form was ornamented 
with obliquely arranged spines of which the nodes on the cast are the 
internal impressions. I am aware of no genus into which the specimen 
would properly fall, but as my literature is by no means complete, I 
hesitate to create a new genus. The genus Thoracoceras' includes longi- 
1 Eich., Bull. Soc. Imp. de Nat. de Mosc., p. 761, 1844. 
