220 PROCEEDINGS OF THE AMERICAN ACADEMY. 



base occupies nearly the entire distance between the bases of the 

 anterior antennae (Plate 2, Figures 20, 21). 



The abdomen of the female is 3-segmented, the genital segment being 

 as long as the other two ; the second segment is a little longer than 

 the third (Plate 1, Figure 4 ; Plate 2, Figure 13). The abdomen of 

 the male (Plate 2, Figure 14) is apparently 4-segmented. The four 

 segments are of about equal lengths. The furcal rami in both sexes 

 are about three and one half times as long as broad. 



The anterior antennae reach to the end of the furca. Both antennae 

 in the female are 25-jointed. The right one in the male is a grasping 

 organ (Plate 4, Figure 35) and is 23-jointed ; the left is 25-jointed. 

 The terminal portion of the grasping antenna is 4-jointed. 



The other cephalic appendages are alike in the sexes. The posterior 

 antennae have the inner ramus shorter than the outer ; the former is 

 2-jointed and the latter 8-jointed. The blade of the mandible (Plate 

 3, Figure 26) is well developed and has numerous rather fine teeth of 

 irregular form on the cutting edge. The outer ramus is 4-jointed, the 

 first three joints having each one bristle, the fourth joint having two ; 

 the inner ramus is 2-jointed, the first joint carrying three bristles and 

 the second carrying eleven, as shown in Plate 3, Figure 31. The 

 maxilla (Plate 3, Figure 25) has the rami and lobes well developed. 

 The "outer border lobe" bears a group of three small bristles and a 

 group of seven that are much larger. The outer ramus carries bristles 

 of about equal sizes ; the inner ramus has fourteen bristles altogether, 

 disposed, as shown, in two groups of three bristles each and two of four 

 bristles each. The masticatory lobe has ten of the very heavy spinose 

 bristles and three delicate smooth bristles. The second lobe of the 

 inner margin has five bristles, the third has four, and the second basal 

 has five. The anterior maxilliped is rather short and broad (Plate 3, 

 Figure 28). There are seven lobes on the inner margin ; the number 

 of bristles on the lobes in order is 6, 3, 3, 3, 4, 2, 4. The posterior 

 maxilliped (Plate 4, Figure 38) is slender and weakly developed ; it is 

 7 -jointed, the endopodite containing five joints. The endopodite is as 

 long as the second basal ; the greatest breadth of the first basal is twice 

 that of the second. The first basal has the bristles on the inner mar- 

 gin disposed in four groups, consisting of 1, 2, 4, and 3, respectively, 

 beginning at the base. The joints of the inner ramus have the follow- 

 ing number of bristles on the inner margin, beginning with the first 

 joint : 4, 4, 3, 4, 4. 



The four anterior pairs of swimming feet are alike in the sexes. Both 

 rami in all the pairs are 3-jointed, and the first basal in all has one 

 inner marginal bristle. 



