ISOPODA. 47 



of removing what really belonged to the animal. A strong groove (but not necessarily 

 an articulation) separates the first segment of the perseon from the head. Tbe long 

 fourth segment has a dorsal hump in advance of the middle and a small medio-dorsal 

 tubercle closely flanked by two others a little to the rear of it on the hind margin. 

 The sixth perseon segment appears to have two lateral tubercles, the fifth and seventh 

 segments each one such tubercle on either side. No transverse dorsal divisions of the 

 pleon could be discerned, but on each lateral margin there are three projections ; to 

 the last and most prominent of these a short obtusely ending apical triangle succeeds, 

 very different from the acute ending of the pleon in the four Norwegian species figured 

 by Professor G. 0. Sars, but agreeing with the apex in A. granulata, Sars, and 

 A. marionensis, Beddard. 



The first antennae are normal, with stout first joint, the second and third 

 successively narrower, the one-jointed flagellum fringed with thirteen or fourteen 

 sensory filaments. 



The second antennas are very little shorter than the body, the third joint much 

 stouter distally than at its base, the fourth joint the longest of all, but much narrower 

 than the third and curving to a little conspicuous tooth not far from the base ; the 

 fifth joint is narrower, intermediate in length between the third and fourth, about 

 twice as long as the three-jointed flagellum. 



In the mouth parts and limbs there is scarcely any tangible difference from the 

 corresponding structures figured by Sars for A. lovgicomis (Sowerby). 



On one of the mandibles, between the accessory plate and the strong molar, in this 

 species two or three short spines are to be seen crowded into a very narrow space. 

 The cutting edere has three or four close-set teeth. The first maxillae have three setae 

 on the inner plate, nine very short spines on the outer. The second maxillae have the 

 inner plate much broader and more setose than the other two plates. In the maxillipeds 

 the broad plate of the second joint is armed with a remarkably large coupling hook ; 

 the seventh joint is well developed, not unguiform. 



The first gnathopods, of which the last four joints are by no means unlike the 

 corresponding four of the maxillipeds, have serrate spines on the broad fifth joint. 

 The seventh joint has one conspicuous spine among many that are smaller. The 

 second gnathopods and the first and second peraeopods are, as usual, alike, very 

 slender, with the seventh joint minute, this and the three preceding joints being 

 furnished with very long setae. The fourth, fifth and sixth joints are subequal in 

 length. The third peraeopods are a little longer than the fourth or fifth, all three 

 pairs being stoutly built, with the second and sixth joints longest, but none very 

 elongate or conspicuously armed, except the finger which has a stout apical tooth on 

 the inner margin in addition to the short curved nail. The finger is also tuberculate 

 on the inner margin, and this is perhaps the case with some of the preceding joints. 



The pleopods agree very nearly with those which have been figured by Sars for the 

 male of A. longicomis and A. granulata, the first two pairs having slender rami, with 



