16 CARL BOVALLIUS, THE OXYCEPHALIDS. 



the telson and the last ural segment. The likeness between the Xiphoce- 

 phalidce and the Caprellids, suggested by previous authors, is very super- 

 ficial and is no reasn for placing the Xiphocephalidce last in the tribe 1 ). 



C. Characteristics for the distinction of the Genera among the 



OXYCEPHALIDS. 



1. The general form of the head and the rostrum. 



2. The first pair of perceopoda being simple, subcheliform, or cheliform t 



3. The second pair of perceopoda being subcheliform, or cheliform. 



4. The inner rarni of the second and third pairs of uropoda coalesced 



with the corresponding peduncles, - - or free. 



5. The relation between the length of the ural segments. 



These five characteristics are sufficient for the distinction of the 

 genera given here below as constituting the family Oxycephalidce. 



D. Characteristics for the distinction of the Species of the 



OXYCEPHALIDEAN GENERA. 



These characteristics vary of course much in the different genera, 

 but a few which are very useful and of common occurence may be 

 pointed out here. 



1. The armature of the first two pairs of perosopoda. 



2. The seventh pair of perceopoda. 



3. The relation between the outer and inner rami of the uropoda. 



4. The relation between the telson and the last ural segment. 



Within the genus Xiphocephalus particularly the following good 

 specific characteristics may be indicated: 



1. The form of the epimeral of the first pair of perceopoda. 



2. The form of the lateral parts of the seventh perceonal segment. 



3. The relation between the length of the first two pairs of uropoda. 



4. The relation between the last pair of uropoda and the telson. 



1) For further information on these points see my forthcoming paper Remarks 

 on the system and synonymy of the Amphipoda Hyperiidea. 



