XiphocephalidjE. 115 



The urojjoda are provided with rami. 



The tt'lson is not coalesced with the last lira! segment'). 



Characteristic features of this family, in addition to those given 

 in the diagnosis, are the enormous development of the auditory vesicles 

 in the hind part of the head, the not less highly developed glands in some 

 of the joints of the perfeopoda (see above, p. 42), and also the peculiar 

 manner of bearing and protecting the eggs and young ones (see above p. 

 31 and 43). The most striking among the external characteristics is the 

 extreme elongation of the head and the urus, with its appendages, but 

 notwithstanding this there are very few details showing analogies with 

 the other elongated forms of Amphipoda, viz: Tanaidea and Caprellidea. 



The first description of an animal belonging to this family was 

 published in 1840 by H. Milne Edwards (7, see above p. 3). In the 

 following year Eydoux and Souleyet (8, p. 267) gave a detailed descrip- 

 tion of an Oxycephalid, which they supposed to be identical with the 

 O.n/ceplialns annatus of H. Milne Edwards. The drawing which 

 they gave, is the first we have of a Xiphocephalid, and in execution 

 has not been rivalled to this day; a copy of it in reduced scale is given 

 below (PI. VII, fig. 1). In the work of these authors we also find the 

 first recognition of the animal in question as the type for an indepen- 

 dent genus. According to their statement it was F. E. Guérin-Méneville, 

 who proposed the new generic name Xiphocephalus. He did not give 

 a full diagnosis, it is true, but the identity of the genus there was no 

 possibility of mistaking, as the description of the species was exhaustive, 

 and the accompanying drawing excellent, as I have mentioned above. 

 From this generic name the present family-name has been taken. 



An exception is Xiphocephalus brevicaudatus, Th. Stebbing. 



