CRUSTACEA. 
69 
AC IDAS PI D^. 
ACIDASPIS, Murchison. 1839. 
Aciuaspis callicera, n. sp. 
PLATE XVI B, FIGS. 1-13. 
General Form and Outline. Body ovate; anterior margin slightly transverse; 
lateral margins evenly converging from the base of the cephalon. 
Surface convex along the axis, depressed on the pleurm. Length to width 
as 4 to 3. 
Cephalon transversely sub-rectangular, anterior and posterior margins sub¬ 
parallel, lateral margins divergent at the genal angles. Width equal to 
rather more than twice the length. 
Facial Sutures beginning on the posterior margin, just within the genal 
angles, passing inward and forward over the eye-lobes, thence forward, con¬ 
verging slightly to the frontal margin. 
Glabella sub-quadrate, frontal lobe elongate, convex, elevated, extending 
from the frontal margin to the occipital furrow; sides parallel. Lateral lobes 
in two pairs, pyriform, the posterior pair the larger, and both separated from 
the frontal lobe by elevated furrows. The lateral lobes are included by a 
ridge which extends from the anterior limb of the frontal lobe to the 
eye and thence to the axial furrows. Occipital furrow narrow, becoming 
rapidly obsolete upon the cheeks. Occipital ring broad, arched and bearing 
a short central spine. 
Cheeks broad, slightly concave and sloping abruptly from the elevated eye- 
lobes. Border moderately thickened and produced at the genal angles into 
long, slightly incurved, diverging spines; above this the margin is fringed 
with short spines which are reduced to mere denticulations in front. 
