322 Transactions. 



specimens to Haswell's species, accepting the view that the males presented 

 some, variety of form in the second, gnathopoda. The form described and 

 figured by him closely corresponds with that of my Port Jackson specimens. 

 He placed the species under the genus Elasmopus Costa. 



In 1904 Walker referred specimens from Ceylon to Elasmopus sub- 

 carinatus (Haswell). drawing attention to differences among them in 

 the second gnathopoda of the male, all of them having the hind margin 

 densely setose, but none being quite like the one figured by Stebbing in the 

 " Challenger " Report. In 1909 he assigned specimens from Cargados, in 

 the Indian Ocean, to the same species; in these he savs the wrist and hand 

 of the second gnathopoda of the male " have an inflated appearance, and 

 are almost naked. It appears to be the form described by Chilton (Proc. 

 Linn. Soc. N.S.W., vol. ix, part J) under Moera petriei, which he unites 

 with this species ; it is probably a condition of immaturity." In 1910 

 Stebbing recorded the species from Cape Colonv, and says that a small 

 male has the second gnathopod agreeing with that described and figured 

 by Walker in 1901 from a Ceylon specimen. 



If the specimens from these different localities are all rightly referred to 

 Elasmopus subcarinatus, the species is a widely distributed one in Indian 

 and Southern Oceans, and presents considerable differences in the form of 

 the second gnathopoda of the male. I have never felt quite certain whether 

 these differences were merely stages of growth in the development of the 

 mature form, or whether we were dealing with a species with dimorphic 

 males, or, again, with two different species with similar females but different 

 males. Caution is necessary in coming to a conclusion, for there are other 

 closely allied species of Elasmopus with male gnathopoda not unlike the 

 setose form described by Thomson, Stebbing, and Walker ; thus New Zealand 

 specimens that I at first sight thought belonged here prove to differ also 

 in the carination of the pleon, and to belong to the species E. neglectus, 

 described below. Nearly all the forms I have personally collected in 

 New Zealand have the male gnathopoda like that described by me under 

 Maera petriei — i.e., not densely fringed with long slender hairs. Thomson's 

 Stewart Island specimens, on the other hand, have the gnathopoda densely 

 fringed, as in the Port Jackson and " Challenger " specimens, and I have 

 a similar specimen from Moko Hinou ; so that the two forms do occur in 

 New Zealand, and if Walker's identification of the Cargados specimen is 

 correct the two forms also occur in the Indian Ocean, though they apparently 

 have not been taken together. In the typical adult male second gnathopod 

 as figured by Stebbing in the " Challenger " Report the palm shows distinct 

 teeth and the hind margin in densely setose ; in adult forms like this the 

 posterior peraeopoda are particularly stout, and their terminal joints very 

 setose. In younger specimens transitional stages in the development of these 

 two characters are to be found, and the forms described by Walker, Stebbing, 

 and Thomson are, I think, males of this form, some of them not yet fully 

 developed, in which the teeth on the palm are less prominent, though the 

 long slender setae are already present. In the gnathopod of the males de- 

 scribed by me under Maera petriei the palm is differently toothed, and the 

 long slender setae are entirely absent, though a few ordinary setae are present. 

 This form occurs in specimens quite as large and apparently as fully deve- 

 loped as those with the setose gnathopoda, and from their difference in shape 

 it is, I think, impossible to look upon them as stages leading up to the fully 

 developed setose form. I consider them to be a different form of the male, 



