252 Canadian Record of Science. 
quite around the outer margin of the cheek; a lighter 
furrow crosses the ocular fillet diagonally causing the fillet 
to assume in some examplesa tubercular form. There is also 
a minute tubercle on the occipital ring. 
The ocular lobes were wanting in the specimen on which 
the original description of this species was founded, and it 
was not recognized as an Ellipsocephalus, and even now 
that the head is completely known, the agrauloid features 
of the glabella are remarkable; this part of the head is 
slightly conical, is somewhat angulated in front and has 
furrows, all of which are directed strongly backward. The 
posterior glabella furrow, in well preserved examples, 
shows a thread-like extension, which turns backward and 
outward and reaches the occipital furrow: the second fur- 
row is prolonged backward until the two parts almost meet 
on the axis of the glabella at an acute angle. 
There is considerable variation in the surface markings 
of this species ; sometimes the raised lines on the front area 
are absent, the glabellar furrows are obscure and the sur- 
face of the test generally smooth. This may have been 
caused by the wear of the crusts as they lay scattered on 
the sandy bottom ; for as the heads of different species are 
found packed within each other, they seem to have been 
rolled or washed about on the bottom of the sea before 
entombment. 
Comparison with other species—Protolenus. 
Under the name of Olenus, Prof. G. Meneghini some 
years ago described two species of trilobites from the Cam- 
brian rocks of Sardinia, which resemble the species the 
writer here places under the generic name Protolenus. 
Although referred by Meneghini to Olenus, in many re- 
spects these species of Sardinia differ from that genus, yet 
both are evidently of the family of the Olenide. Their long 
eyelobes associate them with the Acadian species described 
above; one (O. armatus) is rather imperfectly known, but the 
other, O. Zoppii (Fig. 3), is well shown by various figures 
