38 
MUSEUM BULLETIN No. 31. 
Genus, Calymene Brongniart. 
Calymene sp. ind. 
Plate XI, figure 5. 
This very young individual of an undetermined speeies of 
Calymene from the soft, light-coloured shale above the Collingwood 
at Craigleith, is figured to call attention to an important feature in 
the development of this genus. The facial sutures in the adult cut 
the genal angles exactly as they do in Triarthrus , making it difficult 
to determine from this characteristic alone whether the genus should 
be referred to the Opisrthoparia or Proparia. In the development, 
however, as shown by young specimens, the cheeks are first decidedly 
Proparian, and the posterior portion of the facial sutnre reaches the 
margin in front of the genal angle. 
Genus, Pterygometopus Schmidt. 
Pterygometopns achates (Billings). 
Plate XI, figure 3. 
Dalmamtes achates Billings. Can. Nat. and Geol., vol. Y, 1860, p. 63, 
fig. 9. For further references see Bassler, Bull. 92, TJ.S. Nat. 
Mus., 1915, p. 1065. 
This species, characterized by the broadly oval frontal lobe of the 
glabella, was described originally from the middle Trenton, but seems 
to have a considerable vertical range. It is one of the most common 
species in the Eimmswick of Missouri (lower Trenton), but the 
specimen figured is from the Cobourg (upper Trenton) at Picton, 
Ont. 
