g46 CRUSTACEA. 



Family ORCHESTIAE. 



The dissimilarity between the sexes in the Orchestidae has pro- 

 duced some confusion in the genera as well as species of this family. 

 Fr. Miiller was the first to point out that the females have sometimes 

 the characters of one genus, while the males have those of another * 

 The Talitri have been characterized as having a styliform or ungui- 

 culate termination to the first pair of feet and no proper hand to the 

 second pair, while the Orchestiae have a hand to these legs, more or 

 less distinct. It is now shown, and our own observations sustain it, 

 that the females of certain Orchestise are true Talitri; and M. Miiller 

 hence brings the genera together in one which he calls Orchestia, this 

 name being appropriated hitherto to much the larger group. The 

 styliform or unguiculate termination of the legs of the first pair is the 

 best characteristic of the old genus Talitrus ; those of the second pair 

 have hands, although small and imperfect. 



In tbe species of Orchestia most widely distinct from Talitri, the 

 first and second pairs have distinct hands ; the first pair more or less 

 small or rudimentary. In others, the males are true Orchestise, with 

 hands to both of these pairs, while the females have hands only on 

 the second pair; Talitrus-like, the first pair terminates in a claw 

 not closing against the preceding joint. There is, beside these, a 

 third group, in which both males and females have the first pair of 

 legs without hands, and ending in a claw. In other words, in one 

 group, the individuals of both sexes are Orchestise; in another, the 

 males are Orchestiae and the females Talitri ; in a third, both sexes 

 are Talitri. The transition to the Talitrus-form in the female 

 Orchestiae is very gradual. The finger of the small anterior hands, 

 which closes against the apical margin of the preceding joint or hand, 

 is, in the first step of the transition, a little longer than this margin ; 

 in the next, it is considerably longer, and only the basal portion of its 

 inner side closes against the margin ; in the next, it stands upon the 

 whole breadth of the extremity of the penult joint, and has no power 

 of flexing against any portion of the joint, in which case the leg is 

 unguiculate, if the last joint is small like a claw, and styliform, if 

 rather stout and nearly or quite straight. 



* Archiv fur Naturgeschichte, 1848, p. 53. 



