MEDINAN^ NIAGARAN, AND CHESTER FOSSILS 
113 
One of the small cranidia is 4 mm. in length, but it is well 
preserved. 
Cyphaspis spinulocervix Sp. nov. 
Plate XIV, figs. 4 -d,, B, C 
Three specimens belong to the type series. Of these only one 
presents the long nuchal spine, and this specimen must, therefore, 
be considered the type. 
Glabella 1.5 mm. in length; 0.75 mm. in width posteriorly, 
including the lateral lobes, 0.8 mm. in width along the neck fur- 
row, excluding these lobes. The lobes are 0.6 mm. in length. 
The width of the neck-ring is 0.2 mm., and the nuchal spine 
extends 1.8 mm. beyond the posterior margin of this ring. The 
spine is long and narrow and starts off abruptly from the pos- 
terior margin of the ring. The glabella is strongly convex, and 
only the posterior margin of the area intervening between the 
glabella and the anterior border of the cranidium is shown. 
The second specimen retains only the point of attachment for 
the nuchal spine, but the spine itself is missing. The remainder 
of the specimen, however, is well shown. The length of the 
cranidium is 4.1 mm. Of this length 2.5 mm. belongs to the 
glabella, 0.4 mm. to the neck-ring, and 1.2 mm. to that part 
of the cranidium which is in front of the glabella. The width 
of the glabella including the lateral lobes is almost 3 rnm.; ex- 
cluding these lobes its width posteriorly is 1.4 mm. The length 
of the lobes is 0.9 mm. Their form is ovate. The space between 
the anterior margin of the glabella and the anterior border of 
the cranidium is 0.8 mm. in length, 0.4 mm. being occupied by 
the anterior border. A narrow, deeply impressed groove bor- 
ders the anterior and antero-lateral parts of the glabella. In- 
mediately anterior to this groove the cranidium is distinctly 
convex antero-posteriorly. A similar narrow groove borders 
the posterior margin of the anterior border of the cranidium. 
This border inclines upward and forward at an angle of about 
135° with the general horizontal plane of the cranidium. The 
glabella, its lobes, and the area intervening between the glabella 
and the anterior border of the cranidium are relatively coarsely 
