Page:Transactions NZ Institute Volume 15.djvu/103

radiata. It affords a very good example of protective resemblance, for the body being very flat and of a brown colour can scarcely be distinguished from the seaweed, to which it closely adheres. It has several appliances which enable it to cling tightly to the seaweed; in the first place all the legs are furnished at the ends with powerful hooked claws, then on the under side of the basal joint of last pair of pleopoda and round the proximal edge of the outer branch are strong hooked setæ, and besides this, on the basal joints of all the legs, on some parts of the under surface of the head and in one or two other places, are small projections of the integument which may possibly be hooked setæ, though their nature is not very apparent, but which certainly appear to have the same function. They are shown on the basal joints of the legs in fig. 5 d and f.

In the mouth parts the maxillipedes appear to have the same form as in Sphæroma, etc., consisting of a long slender basal portion bearing an appendage of four joints, none of which is produced into a lobe at the distal end. The maxillæ I have not made out satisfactorily. The mandible is long and slender and has a sharp cutting edge of four teeth, and below two setæ with stout bases. There is no appendage unless a rounded protuberance on the mandible itself is to be regarded as such (fig. 5 c).

The branchial plates—pleopoda—rest in a slight hollow formed by the arching of the abdomen. There appear to be two distinct kinds, the first (fig. 5 g) consists of a short basal joint bearing two long subequal joints, each of which bears several long plumose setæ; in the second (fig. 5 h) the basal joint is about twice as broad as long, the inner branch is short and triangular, the inner edge straight and the outer one slightly curved, it has no setæ except a few exceedingly delicate ones along the inner edge; the outer branch is of the same length as the inner, and is curved so as to fit along the curved outer edge of the inner branch, it bears short plumose setæ along its outer edge, these start about half-way along the joint, and are at first very small, but gradually increase in size till the end where they are largest.

When viewed from above the last pair of pleopoda appears to be articulated on to the abdomen at its posterior edge, but when seen from below it will be found that the basal joint extends anteriorly along the under side of the abdomen, and no doubt belongs as usual to the sixth segment of pleon, which is, together with the others, completely united to the terminal one or telson.

At the end of the abdomen, in the centre, there is a small opening formed by the posterior edge of the abdomen being slightly arched and thus raised a little above the inner branch of the last pleopod; at this opening is a kind of strainer formed by setæ on the posterior edge of the abdomen and