CRUSTACEA. 
87 
behind the ocular node, and widening toward the genal angles. Occipital 
ring strongly arched over the very narrow axis. 
Cheeks, as far as known from a single fragment, relatively broad, evenly 
rounded upon the margin, and produced at the angles beyond the posterior 
margin of the shield. 
Thorax. A single detached segment has been observed, which is strongly 
arched upon the axis and slopes rapidly upon the pleurae to the lateral 
margins. It is very narrow and shows no articulating planes toward the 
extremities. 
Pygidium relatively large, flabellate, depressed-convex. 
Axis less than one-third as wide as the shield upon the anterior margin, 
strongly arched upon the first two annulations, becoming depressed poste¬ 
riorly, tapering to an obtuse termination just below the center of the 
pygidium and connected with the posterior margin by an elevated ridge. 
, It bears three distinct annulations and seven transverse rows of pustules. 
The pleum are broad, flattened above, and somewhat abruptly deflected 
near the margins; bearing two distant, elevated, narrow annulations, each of 
which terminates on the margin in a short spine directed posteriorly. There 
is no evidence of other annulations upon the pleurae, but the postero-lateral 
margin bears two other pairs of spines, making in all eight spines in the 
marginal fimbria. Border thickened, narrow uj)on the sides, becoming wider 
at the posterior extremity. 
Surface ornamented with pustules which, on the cephalon, are fine and 
crowded upon the frontal portions and coarser toward the occipital ring. 
Upon the thorax these pustules appear to be arranged in a single row for 
each segment. The annulations of the pygidium each bear a single row, 
and the postero-lateral area is covered with scattered tubercles and granules. 
Dimensions. Average specimens afford the following measurements; 
Cephalon. Pygidium. 
Length__ 6 mm. 9 mm. 
Width_ 6 mm. (between the eyes.) II mm. 
