CRUSTACEA. 117 



Facial Sutures normal. 



Glabella sub-conate, sides broadly tapering to the anterior extremity, where 

 it is closely appressed upon the narrow, reflexed margin. Width three- 

 fourths the length. Surface convex, anterior slope normally abrupl or 

 vertical, curving posteriorly and becoming horizontal at the occipital furrow. 

 Under normal preservation only a single pair of lateral furrows is visible. 

 These are the fourth or basal furrows and are very strong and deep, taking 

 their origin nearly opposite the anterior angle of the eye and extending to the 

 occipital furrow, thus forming two strong conspicuous lobes. Upon casts of 

 the lower surface, and in extremely rare instances upon the dorsal surface. 

 there is evidence of the first, second and third pairs of furrows, with 

 faint indications of the accessory furrows. Occipital lobes prominent : 

 occipital furrow narrow, broadly hi furcating about the occipital lobes, and 

 becoming deeply impressed and broadened upon the cheeks: occipital ring 

 broad and posteriorly convex, narrowing upon the cheeks. 



Eyes not large, lunate; palpebral lobe inconspicuous; palpebral sulcus nar- 

 row and deep. 



Cheeks deeply grooved about the orbit of the eye, and abruptly depressed 

 to the broad marginal sulcus. 



Thorax sub-rectangular; surface convex and equally trilobate; length to 

 width as 1 to 1.8; composed of ten segments which are arched upon the 

 axis and considerably elevated above the pleurae, obliquely flattened and 

 transverse. 



The pleura, are flattened for less than one-half their width and abruptly 

 deflected to the margin: segments sulcate, anterior and posterior limbs nearly 

 equal, the former becoming abruptly obsolete at the fulcrum. 



Pygidium large, semi-elliptical, convex: length to width as 2 to 3. 



Axis having less than one-third the width of the shield upon the anterior 

 margin, and tapering to a blunt termination within the border. Annulations 

 thirteen or fourteen, with an anterior bend near the mar-ins, and a broad 

 curve over the median line; in most individuals, the annulations are slightly 



