1900.] FEOM THE FALKLAND ISLANDS. 557 



on the left than on the right mandible ; molar cylindrical, with 

 spines above, as well as the usual spine-row ; spines on the second 

 and third joints of the palp pectinate. 



First maxillae. — Inner plate narrow, with four plumose setae at 

 the apex, outer plate with a lobe below the middle, and on the 

 apex nine stout, and three slender, somewhat denticulate spines. 



Maxillipeds. — Second joint wide at the base, then narrow, its 

 plate narrow at the base, then wide, the apical margin broad, 

 carrying numerous plumose spines; third joint short; fourth narrow 

 at base, the lobed distal end wide; fifth much shorter but about as 

 wide distally ; sixth longer than fifth or seventh, much narrower 

 than fifth, with a short lobe at its widened distal end ; seventh 

 narrow, not unguiform. The fifth and sixth joints are not without 

 armature of the inner margin, but it is far less conspicuous thau 

 the long setae which those joints display in Splueroma serratum. 



Here, as in Sphceroma curtum, the fifth joint is decidedly smaller 

 than the fourth, but in SpJiazroma rugicauda the fifth joint is 

 larger than the fourth, as in Sphceroma serratum. 



Limbs of the peraeon. — In these there is a gradual increase of 

 length, so that the seventh pair is considerably longer than the 

 first. In all, the third joint is elongate, without the long setae 

 displayed in Sphceroma serratum • the fourth, fifth, and sixth 

 joints are thickly furred along the forward margin, the fourth and 

 fifth having a group of small spines on the backward apex ; the 

 sixth has at the apex, on the inner side, as in various other 

 Sphaeromidae, and in Isopoda of other families, a rounded plate 

 overlapping the base of the finger ; the finger is of the kind called 

 bidentate, one tooth being the short, curved, horny-looking nail, 

 the other a small spine near the base of the nail. 



The appendages of the male on the seventh peraeon-segment are 

 rather long, about four times as long as broad. 



Pleopods. — The first pair are smaller than the second. The 

 male appendage of the second is considerably longer than the rami, 

 apart from their long fringes of plumose setae, and ends almost 

 acutely, not being roundly expanded at the apex as in Sphceroma 

 rugicauda. The covering ramus in the last three pairs has a 

 transverse suture near the end ; the under ramus of the fourth 

 and fifth pairs is much plicated. 



Uropods. — The lower outer branch is a little broader and apically 

 a little more broadly rounded than the inner, which is sometimes 

 spoken of as a prolongation of the peduncle, there being, in fact, 

 no articulation between them. 



One of Mr. Vallentin's specimens is distinguished from the 

 rest as follows : — It has the sides of theperaeon-segments abruptly 

 down-bent, so as to form a sharp angle with the middle of the 

 back ; on the fourth pleon-segment are a pair of little median 

 humps, such as are barely indicated in the other specimens ; the 

 pleon-shield has the median line occupied by a longitudinal groove 

 between two elevations, and then by a carina of which the first 

 part is divided between two tubercles, the remainder running to 



Peoc. Zool. Soc— 1900, No. XXXVII. 37 



