CRUSTACEA. 
65 
The axial portion of the glabella between the lateral lobes is somewhat ele¬ 
vated, terminating in a narrow annulation formed by the coalescence of this 
part with the third pair of lobes. Occipital furrow narrow; occipital ring 
broad and strongly arched. 
Cheeks grooved and slightly flattened beneath the orbital ridge, falling 
away thence somewhat abruptly to the margins. The regular convexity of 
their surface is interrupted only by the sutural grooves. 
Eyes large, closely appressed to the glabella, and more elevated than any 
other portion of the cephalon. Visual surface lunate, lenses abundant. Pal- 
pebrum crescentic, narrow; palpebral lobe sloping rapidly from the coalesced 
first and second lobes of the glabella, from which it is separated by a sharp 
furrow. 
Thorax. Outline sub-quadrate, lateral margins slowly approximating. Length 
and width equal. Surface conspicuously and sub-equally trilobate. 
Axis strongly arched, relatively narrow on the anterior margin, widening 
to the fourth or fifth segment, thence narrowing to the pygidium; segments 
transverse, or with a slight double curve, posteriorly near the margins and 
anteriorly over the axial line. 
Pleurae flattened above for one-half their width, and abruptly deflected at 
the sides. Each segment is strongly elevated near the axial furrow, and con¬ 
spicuously sulcate, the anterior limb, at the fulcrum or line of geniculation, 
being as broad as the posterior limb. The former becomes obsolete upon the 
lateral slope where the planes of articulation are broad. 
Pygidium. Outline sub-triangular, sub-equilateral; width slightly greater than 
the length. Surface convex anteriorly, angulated on the axial line, and on 
the posterior portion sloping abruptly from this line to the margins. 
Axis arched, equal in width to one-fourth the width of the shield, sides 
appressed and sharply angulated upon the median line; evenly tapering to a 
termination, beyond which an angulated ridge is continued to the margin; 
bearing twelve annulations which are low, somewhat flattened and trans¬ 
verse, each one with a short, laterally compressed spine or spiniform node. 
