BY CHARLES CHILTON, M.A. 1041 



Along with the preceding species I took a few specimens wLich 

 I refer without hesitation to M. tenuvpes. One of my specimens 

 was a mature female, and from its close resemblance to M. 

 Mortoni in everything but the anterior gnathopoda, I very much 

 suspect that they are only nrale and female of the same species. 

 We have a similar case among New Zealand Amphipoda where 

 M. maculattis, Thomson, which is certainly a female form, has for 

 male either the form with large anterior gnathopoda which I have 

 described (Transactions New Zealand Institute, Vol. XIV., p. 

 173), or Aora typica. (See Thomson's Trans. N.Z. Inst., Vol. 

 XIII., p. 218.) All three forms are found in Lyttelton Harbour, 

 and though M. maculatus ^, Chilton, and Aora typica very closely 

 resemble one another in other respects they differ constantly in 

 the form of the anterior gnathopoda and in the arrangement of 

 the long hairs thereon. Under these circumstances it is a little 

 puzzling to know whether we are dealing with two species of 

 which the males are distinct, but the females almost or quite 

 alike, or with one species having two forms of the males. Until 

 further evidence is forthcoming I prefer to consider the species as 

 distinct. I have a similar instance with Parancenia. For two of 

 the three species, viz., P. typica (1), and P. dentifera I know 

 only one form of the female, and for the third species P. loivn- 

 majiics I have a female form which very closely resembles the 

 female described for P. typica, but appears to differ from it in a 

 few small points (2). I have also another instance of the same 

 kind in two undescribed species of Lysianassa from Lyttelton 

 Harbour in which the females are almost but not quite identical, 

 but the males considerably different. 



If Jlicrodeuteropus tenuipes is really the female of M. Mortoni, 

 it will be another example of the same thing for it is almost if not 

 quite identical with 31. macidatios 9 Thomson, while 31. Mortoni 

 closely resembles both 31. maculatus ^ Chilton and Aora typica in 

 everything except the first gnathopoda. 



(1). Possibly P. typica, Chilton, is the same as M(era aiiproximaus, 

 Haswell, a species which I had originally overlooked, but neither the figure 

 nor description is sufficiently detailed to warrant me in actually combining 

 the two species without further evidence. 



^2,. See " Transactions N.Z. Institute, Vol. XVI., p. 258." 



