74 STALK-EYED CRUSTACEA. 



they show a little when the aniiual is viewed from above. The basal seg- 

 ment of the anteniijc, moreover, is more exposed from above than it is in 

 the more topical species of 3Iiuiida. 



The lateral rostral spines, or supraocular spines, are curved upward more 

 than the median rostral spine, and the three are nearly parallel ; the lateral 

 spines reach about half wav to the tip of the median ; all three are micro- 

 scopically spinulose on their upper edge. There are two pairs of spines on 

 the anterior part of' the gastric region in line with the lateral rostral spines. 

 Of these two pairs the anterior is the larger. There is also a longitudinal 

 line of spinules in the median line between the two pairs just spoken of. The 

 arrangement of the other spines on the anterior portion of the carapace will 

 be best understood by reference to the figui'e on Plate XVI. The cardiac 

 area is somewliat sunk below the level of the surrounding parts, its anterior 

 margin is denticulated, with a larger spine on each side. The lateral mar- 

 gins of tlie carapace are armed with ten or eleven spines, the one on the 

 antero-lateral angle being the longest. The second abdominal segment is 

 ornamented with a transverse row of eight small spines. The other abdomi- 

 nal segments are normally destitute of spines, but in a few of the many 

 specimens before me there are two or four small spinules on the third seg- 

 ment. The pleura} of the third, fourth, and sixth abdominal segments are 

 acute, the rest blunt. The eyes are large and are provided with rather long 

 cilia on the edge of the cornea. The basal joiut of the antenna is armed 

 with a long and sharp spine which reaches forward bejond the eves ; the 

 second joint also lias a long spine on each side. The chelipeds are long and 

 hairv ; the merus, carpus, and basal part of the propodite are spin}-, the 

 fingers long, slender, the cutting edges straight and finelj' spinulous.* The 

 ambulatory appendages are setose, the upper and lower edges of the merus 

 are spinulose, and there is, moreover, a row of spinides on the outer surface, 

 this external line of .spinules being best developed on the proximal end of the 

 segment; the carpus is armed witli snudl spines on the upper margin and 



• In some of tlic males the chela is broader than in others, and the basal part of the propodal digit is 

 curved so that there is a distinct gap at the base of the fingers, with one or two rather jironiincnt teeth on 

 the base of the cutting edge of the dactylus. This dilTercnce in tiie form of the chela is generally found among 

 the males of the different species of Miiiii/a, and has been referred to by Henderson (Challenger Auoniura, 

 p. 127), as a case of dimorphism. I have elsewhere (Anier. Journ. Sci., 3d Scr., XXVII. 42—11, 18S1) shown 

 that the two forms of the male in the genus Cainliarus arc alternating stages in the life of the same indi- 

 vidual, one phase being assumed (luring the breeding periods, the other during the intervening seasons of 

 sexual quiesecncc. Jules Rounier (Comptes Rendus de I'.Vcad. Sci., C.\I. 9S7, IS90) has shown that the 

 same condition of things exists among the Amphipoda. I have no doubt that the two forms of the male in 

 the genus Munida are to be expkiucd in the same waj. 



