MUSEUM OF COMPARATIVE ZOOLOGY. 101 



curved or hooked at the tip. The mandibles (PI. IV. Fig. 3 a) are robust at 

 base, but slender and acute at the tip. 



In the prehensile, or first three pairs of legs, the merus, carpus, and pro- 

 podus are each armed with a short, curved, blunt spine on the palmar margin, 

 as shown in the figure of a leg of the first pair on Plate IV. Fig. 3 d. The 

 remaining four pairs of legs, not all natatory, are well fitted for prehension by 

 their slender curved claws, and differ considerably in their proportions in speci- 

 mens of different sizes, as shown by the accompanying table of measurements. 

 All the legs are strongly flexed at the articulation of the basis with the ischium. 

 In the sixth and seventh pairs, the ischium, merus, carpus, and propodus are 

 elongated and in the small specimens slender, so that, with the addition of the 

 dactylus, the last five segments of the leg of the sixth pair may attain to five 

 sixths or even seven eighths the length of the body. The bases do not partici- 

 pate in this elongation and are therefore omitted in the measurements, since to 

 include them would only diminish the contrast between the large and small 

 specimens, shown especially in the last six columns of the table. In large 

 specimens, like the one figured, the sixth and seventh pairs of legs are much 

 more robust than in smaller ones. 



The pleopods (PI. IV. Fig. 3 g) are not naked, as originally described, but 

 all the anterior ones, as usual in the jEgidce, are distinctly ciliated. The cilia 

 are however short and not very evident, and were overlooked in the single 

 specimen described. In the small specimens they are proportionally longer 

 than in larger ones. The second pair of pleopods in the male (PL IV. Fig. 

 3 g) bears a slender stylet tapering to the tip, and about as long as the ramus to 

 which it is attached. In the small specimen, whose measurements are given 

 in the last column of the table, the stylet is blunt, and considerably shorter 

 than the ramus. The uropods (PI. IV. Fig. 3h) are robust; the basal segment 

 is oblique, but not much produced internally; the rami are well ciliated. 



Professor Verrill states that in life this species is bright colored, varying 

 from bright orange to salmon-colored above and light yellow underneath. This 

 color soon fades in alcohol. 



Considerable variations in size, and corresponding variations in the propor- 

 tions, especially of the sixth and seventh pairs of legs, are shown in the fol- 

 lowing table of measurements, in which the first three columns contain 

 measurements of the Blake Expedition specimens, the next four columns con- 

 tain measurements of specimens obtained at a single locality (Station 945) off 

 Martha's Vineyard, by the U. S. Fish Commission in the summer of 1881, 

 while in the last column are measurements of a smaller specimen obtained by 

 the Fish Commission at another locality (Station 1028) in the same region. 

 The measurements in the fourth column are from the specimen figured on 

 Plate III. Figs. 5 and 5 a ; those of the next five columns are from specimens 

 gradually decreasing in size to the last. The length of the ambulatory legs, 

 especially those of the sixth and seventh pairs, is seen to increase proportionally 

 as the length of the body diminishes, except in the case of the seventh pair 

 of legs of the last specimen. This is doubtless to be explained as a mark of 



