262 THE VOYAGE OF H.M.S. CHALLENGER. 



Latreille, the second genus of the Icilinse, is the same as Lfpidactylis, Say, which appears 

 later on as genus 1, of the Poutoporeinre. 



The genus Ovcliestia and its three subgenera, Talitrus, Talorchestia, Orchestia, are defined word 

 for word as in the previous paper, the definition of Talorchestia, therefore, still being, 

 " Pedes Imi luaris ac in Talitro, feminee manu parvula instruct!, " but, to agree with Dana's 

 other statements, and with the facts of the case, the definition of Talorchestia should 

 evidently read : — Pedes Imi fmainm ac in Talitro, maris manu parvula instructi. It is 

 probably owing to this misprint that the British Museum Catalogue speaks of the males of 

 this subgenus as TalUri and the females as Orcliestis. The three subgenera have since 

 been generally accepted as genera. The whole subject is somewhat involved. The genus 

 T'difnis, Latreille, at its first appearance in Bosc. vol. i. p. 78, is thus defined : — " Quatre 

 antennes simples ; les intermediaires superieures, et plus courtes que le pedoncule des 

 laterales et int^rieures ; dix k quatorze pattes." 



" Exemple du genre. Gammarus lorusfa, Fab. — Oniscus (jammavellus, Pallas." 



In vol. ii. p. 148, a fuller definition is given : — " Quatre antennes simples ; les intermediaires, 

 superieures, plus courtes que le pedoncule des inferieures. Corps alonge, couvert de pieces 

 crustacees, transverses, presque egales, et appendicul(5es sur leur cut6s. Dix a quatorze 

 pattes ; les anterieures terminees par des mains. Des appendices bifides a I'extremite du 

 corps." 



In 1813, Leach carved a new genus out of Talifrus, giving for Talitrus the character "Pedes 

 quatuor antici in utroque sexu suba^quales monodactyli ; " for the new genus Orchestia, 

 " Pedum paria quatuor antica monodactyla, pari secundo manu compressa magna, fceminae 

 pari antico monodactylo secundo didaetylo." Thus the original definition of Talitrus is set 

 at naught, and those members of tlie group which have " the anterior feet terminated by 

 hands " are assigned to Orchestia. MUne-Edwards distinguishes the two genera only by 

 the second gnathopods, with a large subcheliform hand in Orchestia, non-prehensile in 

 Talitrus. He takes no notice of the distinction of sex in Orchestia to which Leach refers. 



In 1848 Friedrich MiiUer called attention to the fact that the females have sometimes the 

 characters of one genus, while the males have those of another, the females in certain 

 Orcliestix being true Tcditri. In Dana's words and according to Dana's definitions, " in one 

 group, the individuals of both sexes are Orchestic ; in another, the males are Orchestiae and 

 the females Talitri ; in a third, both sexes are Talitr!. 



A further complication is introduced into the group by the genus Orchestnidea, Nicolet, or 

 Talitronus, Dana. In this it appears that the females are Talitri, while the males are 

 Talitri in the first gnathopod and Orchestiee in the second. The genus comes therefore 

 nearer to Tcdorchestia than to Orchestia. Dana's generic name was, according to Dana, 

 published in the same year with Nicolet's, but may yield precedence, since Dana rejected 

 his own genus, and, so far as I can make out, dates the publication from the time when his 

 paper was read, rather than from the time when it was technically pid^lished. On p. 1.59.5, 

 among the addenda et corrigenda, he says : — '' Orchestoidea tiiherculata of Nicolet, (loe. 

 cit., PI. II. f. 4) is the author's Talitronus insculptus, and the genus Talitronus was insti- 

 tuted and published by the author on July 1, 1849. The name has been since rejected 

 by him for Orchestia insculpta ; and as Gay's specific name is the older, it will become 

 Orchestia tuherculata. We suspect that his Talitrus Chilensis is what we have considered 

 t"he female of the 0. insculpta." Mecjalorchestia, Brandt, 1851, is an additional synonym. 



The second genus which Dana assigns to the Orchestidae, is clearly distinguished from his first 

 genus, Orchestia, in the following manner : — " Allorchestes ; — Slaxillipedes unguiculati. 

 Antennas Imae minores, basi inferiorum saepissime longiores. Epimerae 5tae 4tis scepius 

 multo breviores." 



Further on, p. 883, he adds to the generic description, "Feet of first and second pairs subchelate. 



