MEDINAN, NIAGAEAN, AND CHESTER FOSSILS 
111 
The second specimen belonging to the type series of this species 
is much better preserved. Including the neck-ring, the cranidium 
is 5.2 mm. in length. The anterior margin of the anterior 
border extends 1.3 mm. in front of the glabella, the groove be- 
tween this border and the glabella being 0.25 mm. The glabella 
tends to be more narrowly rounded anteriorly, and the anterior 
or rostral border also appears more narrowly rounded. This 
rostral border is strongly elevated anteriorly, but its upper 
margin does not rise above the general curvature of the glabella 
antero-posteriorly. 
Notwithstanding the differences noted, the two individuals 
probably belong to the same species, 
Calymene sp. 
Plate XIV , figs. 2 A, B, C. 
Four pygidia of the same general appearance are mounted on 
the same small card, and a fifth specimen, loose, was used for a 
lateral view. The largest of these originally was 4.8 mm. in 
length, 7.8 mm. in width, and had a convexity of slightly over 
2 mm. anteriorly. The axial lobe is 3 mm. in width anteriorly 
and rises 0.8 mm. above the adjacent partte of the lateral lobes. 
The outer part of the lateral lobes curves downward toward the 
margin of the pygidium, but without any reversal of curvature 
on approaching the latter. The downward curvature begins 
along a line corresponding to that described in the case of 
Cyphaspis arkanscCna, but the downward curvature along this 
line is less abrupt. 
The axial lobe bears 2 distinct rings, anteriorly, behind which 
there is one ring which is fairly distinct and another ring which 
is faintly visible; 1 or 2 additional rings may .be barely per- 
ceptible, and 1 specimen shows a seventh ring. The pleural 
ribs on the lateral lobes usually are indistinctly marked, except 
the anterior 2 or 3 pairs, these anterior ribs being grooved along 
their median lines. 
It is the absence of any trace of outward curvature along the 
margin of the pygidium, and the presence of additional discern- 
