CRUSTACEA. 
127 
angles the margin is produced into long, rounded spines which reach to the 
seventh segment of the thorax. Posterior margin nearly straight. 
Facial Sutures normal, curving sharply forward on the anterior margin. 
Glabella elongate-sub-conate, surface depressed-convex; length about one- 
fourth greater than the width. The narrow anterior extremity encroaches 
slightly upon the frontal border. Lateral furrows in four pairs, accom¬ 
panied by the posterior accessory furrows. These furrows are all linear 
and in the specimens at hand are quite faint upon the surface, being made 
more conspicuous by the somewhat translucent test. Occipital lobes promi¬ 
nent, transversely sub-pyriform; occipital furrow narrow and sharply impressed; 
occipital ring broad, somewhat flattened above, and strongly arched. 
Eyes moderately large, lunate; orbital ridge depressed and strongly sili¬ 
cate at its base. Palpebral lobe large and closely appressed against the 
glabella; palpebral sulcus narrow and elevated. 
Cheeks depressed at the summit and rounding more or less abruptly to the 
posterior and lateral margins. 
Thorax sub-quadrate, about one-third longer than wide; lateral margins round¬ 
ing to the pygidium. Surface sub-equally trilobate. 
Axis convex and arched, having about one-third the width of the thorax, 
attaining its greatest width at the fourth segment, whence it tapers regularly 
to the pygidium. Segments narrow and somewhat flattened. 
Pleurce laterally depressed at about one-third their widtli from the axis. 
The segments are conspicuously sulcate, the anterior ridge becoming rapidly 
obsolete beyond the fulcrum. 
Pygidium sub-semicircular in outline, faintly emarginate at the posterior ex¬ 
tremity ; anterior margin with a slight forward curve; width equal to twice 
the length. The border is broad and conspicuous, flattened anteriorly, 
thickened and slightly sulcate behind. 
Axis rather narrow, having less than one-third the width of the shield on 
the anterior margin, tapering rapidly to a blunt and elevated apex within 
the posterior border. It is composed of from eight to ten annulations which 
