REPORT ON THE ISOPODA. 49 



slender, the third joint is greatly elongated and very slender, the fourth joint is of the 

 same diameter as the third, but extremely short ; the flagellum is composed of a very 

 large number of short joints ; the first joint of the flagellum is, however, of considerable 

 length, quite as long as the six or seven following joints. 



The antenna; are, in both specimens, broken off at the third joint, the three 

 remaining joints are short and subequal in length, and furnished with numerous spines, 

 which do not appear, in any case, to be branched like those upon the segments. 



The mandibles have a well-developed palp. 



Of the thoracic limbs the anterior pair are much shorter than the rest and subcheliform. 

 The first joint is long and somewhat curved ; its surface is comparatively smooth, the 

 two following joints are small and subequal, together somewhat less than the first joint ; 

 the inner margin of these joints is armed with a few stout spines ; the fourth joint is stout 

 and nearly as long as the first joint ; the inner margin has a row of about a dozen stout 

 spines; the fifth joint is much shorter and more slender, and has only a few delicate 

 spines ; the last joint of the limb is shorter still and more slender, it terminates in a 

 single short pointed claw. 



The remaining thoracic appendages are similar to each other in structure ; one of 

 these is shown in fig. 10 ; they differ principally from the anterior pair of limbs in 

 the comparative shortness of the basal joint, and in the great elongation of the fourth 

 and fifth joints. All these limbs are, in consequence, considerably elongated, but there 

 is a slight difference in length between the more posterior and the more anterior pairs, 

 the former being the longer. 



In any of these appendages the first joint is longer than the following joints which 

 are subequal ; the fourth and fifth joints are immensely elongated, the latter being the 

 longer as well as the more slender, the proportionate length of these two joints to the other 

 joints of the limb increases in the posterior appendages ; the sixth joint is short and bears 

 a single slender claw at its extremity. The limbs are very spiny, more particularly the 

 fourth and fifth joints ; the spines are borne on short tubercles arid are never branched 

 like those which deck the thorax and abdomen. The appendages are also finely 

 granulated bike the general body surface. 



In figs. 11, 13, and 14 I have illustrated the three anterior pairs of abdominal limbs 

 (of the male). 



The first pair were unfortunately broken in detaching them from the animal. They 

 consist of two flattened, closely applied oblong plates, the lateral margins of which are 

 fringed anteriorly with slender hairs. The posterior extremity of this appendage is 

 shown, more highly magnified, in fig. 12; the postero-lateral margin projects slightly, 

 and this region of the appendages (b) is grooved, being evidently rolled up in a scroll- 

 like fashion, the open lips of the groove are beset with slender hairs ; anteriorly these 

 hairs are set in tufts, radiating outwards from a common centre. The posterior 



(ZOOL. CHALL. EXP. PART XLVIII. 1886.) Bbb 7 



