REPORT ON THE AMPHIPODA. 1185 



this family, Gerstaecker expressly says that " the last two segments of the perseon are 

 not coalesced." But the impediment remains that in both Platophium, Dana, and 

 Cyrtopluum, Dana, the fourth and fifth segments of the pleon are not coalesced, and no 

 one of the three pairs of uropods is wanting. The requisite alteration of the definition of 

 the family has been already discussed. 



Platophium ddnse, n. sp. (Pis. CXXVIII., CXXIX.). 



Head without a rostrum, the lateral lobes angled ; below and behind them each side 

 of the head deeply emarginate for the insertion of the lower antennas ; in the middle of 

 the back of the head there is a large upstanding process ; each of the segments of the 

 perseon and of the first two of the pleon is armed with a medio-dorsal carinate tooth or 

 process, which on the first segment of the perseon is small and supplemented by a 

 second ; the tooth on the second segment is also small, larger on the third and fourth, 

 and again considerably larger on each of the following five segments ; the lateral margins 

 of the third, fourth, fifth, and sixth perseon-segments are tridentate, the edges of all the 

 perseon-segnients more or less projecting beyond the side-plates; the seventh of the perseon 

 has a tooth on the hind margin on each side below the dorsal process ; in this the first 

 and second pleon-segments resemble it ; the postero-lateral angles of these and the third 

 segment are rounded ; the third has a transverse dorsal depression ; the fourth pleon- 

 segment is narrow and elongate, tending to cylindrical, with a transverse dorsal depression 

 near the base ; this segment is perfectly distinct from, and has the dorsal margin raised 

 above, the fifth segment ; the fifth and sixth segments are together much shorter than 

 the fourth. The pleon from the fourth segment is strongly flexed. The skin in many 

 parts is furred with short hair. 



The Eyes very prominent, hemispherical, projecting just behind and partially on the 

 lateral lobes of the head ; the ocelli numerous. 



Upper Antennas. — The first joint rather thick, not so long as the head, with slender 

 spines, chiefly at the lower apex ; the second joint thinner, twice as long, with a dozen 

 pairs of long, slender, slightly feathered spines ; the third joint rather shorter and thinner 

 than the second, with ten pairs of the like spines ; the flagellum of nine or ten joints, 

 together not so long as the first and second of the peduncle united, apically carrying 

 groups of cylinders and some spines much shorter than those of the peduncle ; the first 

 joint much longer than the rest, with three or four groups of cylinders ; the secondary 

 flagellum of one joint, narrow, slightly tapering, not so long as the first of the primary, 

 armed with a few setules. 



Loiver Antennas much longer than the upper. The first two joints very short, the 

 gland-cone very small, acute ; the third joint considerably longer than the combined first 

 and second, widening distally, with some slender spines on the lower margin ; the fourth 



(ZOOL. CHALL. EXP. PAET LXVIL 1888.) XxX 149 



