CRUSTACEA. 
149 
Thorax elongate, length to width as 1.3 to 1. Margins tapering with a regular 
curvature. Composed of twelve segments of which the first, fourth and 
sixth are the stronger, the last two being spiniferous. 
Axis broad and arched; width equal to one-third that of the thorax; 
widest at the third or fourth segment and tapering rapidly to the pygidium, 
PleurcB fiattened near the axis for about one-third their width, and sharply 
deflected at the fulcra. Pleural sulci strong; anterior pleural limbs angu- 
lated by the articulating planes, not becoming obsolete on the lateral slopes 
as in most species of this genus. Posterior limbs of the pleural segments 
very strong. 
Pygidium minute; length to width as 1 to 2. 
Axis broad, tapering rapidly to an obtuse termination within the posterior 
margin; bearing two strong annulations, with indications of a third. 
PleurcB deflected, each bearing three double annulations, which become 
obsolete within the slightly thickened margin. 
Surface Ornamentation. Cephalon usually pustulose, the pustules being 
strongest upon the glabella and frontal area. The ornamentation upon these 
parts is often nearly obsolete, and the frontal margin generally quite smooth, 
sometimes with scattered obsolete pustules. The occipital ring, and the 
fourth and sixth segments of the thorax each bear a single slightly recurved 
spine, that upon the sixth segment being much the strongest On the axis 
are four rows of minute granules, two on each side of the median line. The 
fulcra of the pleurae each bear a single row of small bead-like pustules. 
These rows of pustules, upon the axis and pleurae of the pygidium, approx¬ 
imate, and the posterior area is covered with scattered granulations. 
Dimensions. An average entire individual measures; 
Body. Cephalon. Thorax. Pygidium. 
Length_ 12 mm. 3,5 mm. 7 mm. 1.5 mm. 
Width_ 6.5 mm. 6.5 mm. 5.5 mm, 3 mm. 
Fragments occasionally indicate slightly larger dimensions than the above. 
