NYMPHONIDAE 



27 



(Table III), shows that there is no distinctive character, or set of characters, that 

 holds good everywhere. Indeed, exceptions abound — these will be mentioned in the 

 discussion of each separate character — and as no practical advantage is to be gained by 

 retaining a genus that is not definite and distinctive, I have reunited Chaetonymphon 

 and Nymphon as Caiman (191 5, p. 28) and others have done. 



Group I Group II 



The main characters on which I rely for the separation of these groups are found in 

 the male oviger (Table III). In the typical species of group I the fifth segment is long 

 and slender, of approximately uniform diameter throughout, and either straight (type I, 

 e.g. Fig. 10 a and c) or distinctly curved (type I a, Fig. 18 a). In A'^. charcoti the fifth 

 segment is relatively short and more robust, but slightly curved and narrowed proximally 

 (Fig. 10 b). The other four atypical species have the fifth segment long and slender, 

 but distinctly expanded at the distal end though not to the same extent as is typical 

 for group II (type I b, Fig. 23 b, cf. Fig. 27). 



The majority of the species in group II have the fifth segment relatively short, usually 

 more massive than in type I, and clubbed distally (type II, Figs. 23 a, 26 a, c, and 27). 

 In the atypical species, the fifth segment is again short and rather robust, but certain parts 

 of segments 5 and 6 or 3, 4 and 6 are thin-walled, inflated and tend to collapse when 

 the animal is killed and fixed (type II a, Fig. 26 b, and Gordon, 1932, Figs. 10 b and 12 b). 



None of the other characters is of such systematic importance as the male oviger, 

 closely allied species often differing markedly from each other with regard to one or 

 more of these; e.g. the chelophore of A^. paucidens, n.sp., is very difli'erent from that of 

 A^. pfefferi, which not only in its oviger but in most of its other characters closely 

 resembles it. The following survey of these characters follows the order in which they 

 are dealt with in the specific descriptions. 



Trunk. In group I, the trunk is usually slender, non-setose and loosely built, i.e. the 

 lateral processes are separated by at least their own diameter. In A^. adareanum, however, 

 the lateral processes are separated by only half their own diameter. 



In group II the body is usually compact and setose with the lateral processes in 

 contact or separated by narrow intervals — up to half their own diameter. Setae are 

 absent in three species — A^. capense, N. compactum and A'^. articulare ; in A^. australe the 

 lateral processes may be separated by their own diameter. 



The neck is well defined and long, as a rule, in group I, very short in group II ; but 

 in several species of the former it is as short as in the latter group (e.g. A^. pfefferi and 

 A^. adareanum). 



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