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 depression 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 antennæ (antennules) are rather more slender, and are longer, usually reaching to the end of the third joint of the peduncle of the outer antennæ; while in the Tomahawk specimens they do not usually reach beyond the end of the second joint.

4. The outer antennæ 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 specimens 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 Tomahawk Lagoon are usually of a uniform dark greenish-grey.

It is also worthy of note that in none of the Mihiwaka specimens have I found the characteristic setæ found on the outer antennæ 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 considerable 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