AMI'HIPODA — STEBUING, 62J 



single imperfect specimen, I was for a time jjersuadetl that this 

 imperfection had hindered him from recognising the true generic 

 character which was obvious in the specimens of the present 

 species procured by the " Tlietis." This point of view, however,. 

 I have relinquished on reflecting that Haswell claimed for his 

 specimen one of the distinguishing characters of Lcetmalophihts, 

 while he was evidently in ignorance that such a genus had beert 

 established. On transferring his species to it in 1885 he again 

 insists on the chai-acteristic pleon,and adds otherfeatures,saying: — 

 "In this remarkable little species there are only live segments in 

 tlie pleou and only five pairs of appendages. The antennae are 

 subequal and the superior pair have no appendage." 



The general resemblance between Haswell's species and the 

 present member of a nearly allied but distinct genus is further 

 discounted by the circumstance that in the "Thetis" gathering 

 there were included members of the Isopod family Astacillidje, 

 quite deceptively like these Amphipods. That organisms essen- 

 tially different assume a similar garb under similar conditions of 

 existence is not contrary to experience. 



In Fodocerus liystrix the head has a very short triangular 

 rostrum and a large, forward-pointing, medic-dorsal process. In 

 the centre line of the peraeon there are on the first segment two 

 processes, the foremost the larger, pointing forward ; of the three 

 following segments each has an upward-pointing pi'ocess, and with 

 successive increase of size there is a backward directed process to 

 each of the next three segments. Similar processes surmount the 

 first two segments of the pleou, these as well as those on the 

 peraeon being flanked by corresponding rows of acute processes 

 of moderate size. The borders of the peraeon segments are 

 surmounted each by a tubercle and are acutely produced outwards 

 over the side-plates, of which the first pair are sharply produced 

 forwards, and the next three pairs more or less acutely down- 

 wards, while the remaining three have the lower border convex. 



The eyes are dark, sub-globular, prominent at each side of the 

 head, occupying the rounded ends of the eye-lobes, from the top 

 of which a minute point may be seen projecting. 



The first antennse have the second joint much longer than the 

 first, and readily break off between these two ; the third joint is 

 longer than the second or subequal to it ; the flagellum is rather 

 shorter than the second joint of the peduncle, with six joints, of 

 which the first is much the longest. The accessory flagolhim is 

 one-jointed. 



In the much longer second antenna? the fifth joint of the 

 peduncle is longer than tlie fourth, this in turn being longer than 

 the three-jointed flagellum. 



