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. 



Pleurce 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 wdiich an angulated ridge is continued to the margin : 

 bearing twelve annulat'ions which are low, somewhat flattened and trans- 

 verse, each one with a short, laterally compressed spine or spiniform node. 



