CRUSTACEANS. 237 



equaling- the greatest transverse diameter of the glabella in 

 front, but more depressed. Eyes in the form of somewhat 

 oval, ventricose tubercles, considerably lower than the glabella, 

 from which they are separated by rather wide, distinct depres- 

 sions, placed about one-half their length in advance of the 

 posterior margin of the cheeks, and without visible facets; 

 palpebral lobes depressed, not covering the eyes, but merely 

 connecting with their inner sides, so as to leave the visual 

 area forming an almost insolated tubercle. Cheeks sloping 

 from the eyes into a broad deep marginal sulcus, which is not 

 continued around the front of the glabella. Facial sutures 

 cutting the anterior margin nearly on a line with the eyes, but 

 curving so as to leave a small semi-circular wing on each ante- 

 rior lateral margin of the glabella; behind they intersect the 

 posterior margin of the cheeks about midway between the 

 lateral angles and the neck segment, but nearer the latter. 



Thorax nearly as long as the glabella, exclusive of the 

 neck segment, distinctly trilobate ; axial lobe slightly wider than 

 the lateral lobes, rounded and rather prominent ; its segments 

 narrow and straight, or not arched forward. Lateral lobes 

 more depressed, somewhat flattened on the inner side, round- 

 ing down to the lateral margins; segments duplicated by a 

 nearly mesial furrow extending from their inner ends out to 

 or a little beyond the undefined knee, beyond which they are 

 obliquely flattened for folding together and rounded at their 

 extremities. Pygidium a little more than one-fourth wider than 

 long, rather distinctly convex, rounded behind and more or 

 less straight in front, with anterior lateral angles obliquely 

 truncated and a little rounded. Mesial lobe very prominent 

 and well defined, rounded above, and a little flattened or fur- 

 rowed on the sides ; as wide anteriorly as the lateral lobes ; 

 tapering and declining somewhat posteriorly to an abrupt 

 obtuse, prominent termination ; about half its own greatest 

 anterior breadth within the flattened margin ; segments four- 

 teen or fifteen, distinctly defined, smaller than those of the tho- 

 rax. Lateral lobes depressed below the mesial lobe, somewhat 

 flattened on the inner side, and sloping to the rather narrow 



