264 Transactions. — Zoology. 



I have since taken it also in a stream at Waitaki, some 

 miles from Mihiwaka, and on the opposite side of Blueskin 

 Bay. 



On examination these specimens proved to differ from the 

 Tomahawk specimens in several small points. I have already 

 briefly mentioned these in the New Zealand Journal of 

 Science, vol. i. (new issue), p. 131 (1891), but it will be as 

 well to give them here in greater detail. 



1. In the front margin of the head there is a small de- 

 pression in the centre, which makes the middle portion appear 

 more deeply emarginate than the rest of the front margin. 



2. The eyes are much smaller, being only about half as 

 large. 



3. The inner antennas (antennules) are rather more 

 slender, and are longer, usually reaching to the end of the third 

 joint of the peduncle of the outer antenna ; while in the Toma- 

 Irawk specimens they do not usually reach beyond the end of 

 the second joint. 



4. The outer antennae are more slender both in the 

 peduncle and in the flagellum. 



5. There is only one pair of sutures on the terminal segment 

 of the abdomen. In the Tomahawk specimens there are two: 

 the anterior one, though quite distinct, is small, and extends 

 only a short distance towards the median line. The second 

 one is more distinct, and extends nearly to the centre. It is 

 the anterior pair of sutures that is wanting in the Mihiwaka 

 specimens, while the second one, too, is somewhat less distinct. 

 In this respect the Mihiwaka sj)eciraens agree with the figure 

 given by Miers of a Magellan specimen, in which only one pair 

 of sutures is shown. 



6. The extremity of the abdomen is slightly more narrowed, 

 not quite so broadly rounded as in the Tomahawk specimens. 



7. The colour is usually much lighter, being a light-brown 

 with darker spots and markings. The specimens from Toma- 

 hawk Lagoon are usually of a uniform dark greenish-grey. 



It is also W'Orthy of note that in none of the Mihiwaka 

 specimens have I found the characteristic setae found on the 

 outer antennae and on the second pair of legs of the males of 

 the Tomahawk specimens.* 



The differences between the two forms, though not great 

 in amount, are thus seen to be somewhat numerous, and I 

 have found them to be constant by the examination of a con- 

 siderable number of specimens from each locality. Instead of 

 erecting the Mihiwaka form into a distinct species, it will, I 

 think, in this case be more convenient and less misleading if 

 it is given the same name but is considered as a separate 



* See Trans. N.Z. Inst., vol. xxii., p. 195. 



