1336 THE VOYAGE OF H.M.S. CHALLENGER. 



The Perasopods simple, the fifth the shortest, the first four pairs having branchial 

 vesicles ; in the female the first three pairs of peraeopods and the second gnathopods 

 having marsupial plates. 



The three pairs of Uropods having the peduncles longer than the lanceolate rami ; 

 the outer branch shorter than the inner in the first and second pairs. 



Telson very short. 



Head large, tumid, squared in profile, deeper than the peraaon, the mouth organs 

 projecting backwards from the lower hinder corner ; body dorsally compressed. 



Perseon narrowing towards the seventh segment, sometimes becoming tumid at the 

 third segment. 



The eyes to some extent agree with those of Phronima, in that the grouping of the 

 ocelli justifies the expression of divided-eye for each of the pair. In the upper 

 division the ocelli are arranged almost in parallel rows, in the lower and smaller in a 

 radiating manner ; in both, as Claus observes, they stand wide apart. 



Bovallius is inclined, though not without doubts, to unite the genus Daira, Milne- 

 Edwards, 1830, with Paraphronima, Claus, while decidedly and with good reason 

 separating both from Dairinia [Dairilia], Dana. In 1885, to explain his views on 

 these points, he gave parallel descriptions of the three genera mentioned, but in the 

 adaptation of them to a uniform terminology, some obscurity has arisen. The original 

 definition of Daira has been already quoted in the Note on Milne-Edwards, 1830 

 (p. 143). In 1830 Milne-Edwards says that his Daira gabertii is probably not 

 adult, that it has but one pair of antennae, much like the lower antennae in Hyperia, 

 that the first segment of the perseon is extremely short (etroit 1 ) and almost entirely 

 concealed under the second, that the second gnathopods end in a sort of didactyle 

 hand, the movable finger of which extends a little beyond the immovable finger, 

 and is apically armed by a crooked and movable nail, and that the first gnathopods, 

 though similar to the second, have the immovable finger less developed. I cannot 

 therefore see any probability that Daira is the same as Paraphronima, since in the 

 latter there are two pairs of antennas in both sexes, the first segment of the perseon is 

 not at all concealed under the second, the second gnathopods are less stout than the first, 

 while neither pair has any immovable finger at all, the second pair not even having any 

 spines which might by chance be mistaken for one. Bovallius, it is true, among the 

 characters in the definition of Paraphronima, Claus, gives the following : — " The last 

 joints of the second pair [of gnathopods] forming a didactyle hand, the moveable finger 

 consists only of the last joint, and is longer than the fixed one." Claus' own description, 

 however, contains nothing of this sort, and the " fixed " finger probably refers to the 



1 That ttroit refers to the measurement of the segment from front to hack, not from side to side, seems clear from 

 the description of the person, " le thorax point enfie aa milieu comme dans l'Hype>ie de Latreille, mais diminuant 

 progressivement de volume d'avant en arriere." 



