XiPHOCEPHALUS ARMATUS. 123 



The perœon. The first segment is two-thirds as long as the sec- 

 ond; the third, fourth, fifth, and sixth are equal in length; the seventh 

 is only a little shorter than the sixth. 



The epimeral of the first pair of perœopoda (PI. VI, fig. 6) is 

 free from, and articulating with, the first segment; it is deeper than long, 

 evenly rounded, almost tongue-shaped, and has the front margin serrated. 

 The epimerals of the following pairs are coalesced with the correspond- 

 ing segments ; those of the second, third, fourth, and fifth pairs have the 

 imder margin almost straight and sligthly serrated, and the corners ob- 

 tusely rounded ; that of the sixth pair has the hind portion somewhat 

 deeper than the front part, and circularly rounded; the epimeral of the 

 seventh pair (PI. VI, fig. 5) has the under margin dumbbell-shaped, as 

 Streets justly remarks (26, p. 289), the hind portion being less deep 

 than the front part, and circularly rounded. 



The branchial vesicles are very large, tumid, elongate-eggshaped. 

 and attached to the second, third, fourth, fifth, and sixth pairs of perfeo- 

 poda in the male, as well as in the female; that of the second pair is 

 longer than the whole leg, those of the following pairs are a little shorter 

 than the corresponding femora; those of the fifth and sixth pairs are 

 thicker, and more tumid, than the preceding. 



The perceopoda. The first pair (PL VI, fig. 7, and p. 34, fig. 

 57) are very short, and are, when folded up, almost concealed by 

 the large epimeral; the carpus is very broad; the carpal process is 

 triangular, much longer than the stem of the carpus, and has a large 

 sharp tooth at the middle of the hind margin; the front margin is ser- 

 rated, and is much longer than the hind margin of the metacarpus, 

 reaching about to the apex of the dactylus; the hind portion of the 

 metacarpus forms a thin sharp edge, and has the lower corner triangular- 

 ly produced and sharp-pointed; the dactylus is stout, curved, and about 

 three-fourths as long as the metacarpus. The second pair (PL VI, 

 fig. 8) are a little longer than the first, and have the carpus com- 

 paratively less dilated; the carpal process is somewhat curved, and 

 reaches fully to the apex of the dactylus. The third and fourth 

 pairs (PI. VI, fig. 9) are similar in shape, but the fourth is somewhat 

 longer; the femur is linear, about five times as long as broad; the tibia 

 is longer than the femur, is linear in the male, and often also in the 

 female, being about five or six times as long as broad; but in the ovi- 

 gerous female the joint is more or less inflated, containing highly de- 

 veloped glands. The femur of the fifth pair is a little dilated, being 



