2 Trans. Acad. Sci. of St. Louis 



wards from the tip of the head to the third thoracic 

 somite. Thence it extends almost horizontally to about 

 the middle of the last thoracic somite, from there sloping 

 abruptly to the abdomen. The cervical suture is distinct. 

 Each latero-caudal margin of the thorax is produced out- 

 ward and armed with two nipple-like tubercles (pi. 1, fig. 

 Ic; pi. 3, fig. 4b). About the middle of the ventral surf- 

 ace of the first abdominal somite, and located nearer the 

 sides than the middle line, there is a pair of long curved 

 spines, somewhat larger than the tubercles (pi. 2, fig. 

 2f). The outed ramus of the fifth foot is two-jointed (pi. 

 3, fig. 5). The subrectangular first joint is twice as long 

 as wide ; for two-thirds its length the second joint is al- 

 most straight on its outer edge, the inner margin taper- 

 ing gradually from its base to that point ; there the foot 

 abruptly turns inward at an angle of more than 45°, 

 terminating in a blunt point. On its lower third it bears 

 three spines. The inner one, which extends to the angle 

 in the segment, is the longest ; the next about half this 

 long; and the outer one somewhat shorter than the in- 

 termediate one. The inner ramus of the fifth foot is 

 straight and about five times as long as wide ; at its tip 

 are two setae which are about half as long as the ramus. 

 The outer margin, on its distal third, is distinctly hairy. 

 The specimens so far found are of a dirty white color. 



Description of the male. {pi. 1, fig. 2). — The male is 

 about four-fifths the size of the female ; the tubercles on 

 the laterocaudal margin of the thorax are absent or in- 

 conspicuous ; there is no armature on the first abdominal 

 somite. The first basal joint of the right fifth foot is 

 short, about as long as broad (pi. 3, fig. 1) ; the second 

 basal joint is about twice as long as wide and fully twice 

 as long as the preceding joint. The inner ramus (endop- 

 odite) is missing; the outer (expedite) is composed of 

 two joints of about equal length. The first of these joints 

 is about the same length as the second basal segment but 



