BY E. A. BRIGGS. 77 



|ieraeon segments 2-4, pleou in tlie male with three, iu the 

 t'finale with two pairs of appendages. 



St ebbing gives the following key. which serves to distin- 

 guish the three species: — 



1 /'Body smooth . 1. Lodecas elongata, Stebbing. 



l^Body with spiue-like processes — 2. 



Body of male six-s[dned ; flagellum of first antennae 

 seven-jointed. 



2. Dodecas hexaceiitntm, Mayer. 



Body of male ten-spined ; flagellum of first antennae 

 more than seven-joiuted. 



3. Dodecas decacentrum, Stebbing. 



Dodecas decacentrum, Stehh 



iny. 



Dodecas decacentrum, Stebbing, Mem. Austr. Mus., iv., 12, 



lylO, p. 629, pi. Ix. 



This species is characterised by the presence of ten spines 

 in a continuous line of pairs on the dorsal surface, and by 

 the extreme leugtli of the first antennae. The male has a 

 dorsal pair of spines at the end of the first segment, one pair 

 in the mid ^le and one lydh at the end of the second, and two 

 other pairs, arming the third and fourth segments re- 

 spectively at tiie middle. The first antennae are very long, 

 and in the male the last joint of the peduncle is longer than 

 the penultimate. The flagellum contains seventeen to 

 eighteen joints, which are slender and elongate, the first 

 always the longest. The second antennae are slender with 

 the last joint of the peduncle longer than the penultimate. 

 The slender flagellum is composed of seven or eight joints. 

 The mouth-organs are very like those of Dodecas elongata, 

 Stebbing. The eyes are rounded and very prominent. The 

 first gnathopod is of the ordinary type ; in the second, 

 especially in the male, the fifth joint is long and slender, 

 distinct from the sixth, but without sejjarate mobility. The 

 palm of the sixth joint has two emarginatious, of which the 

 distal one is the longer, being veiled by a transparent 

 membrane. The jjleon carries at the base a ventral median 

 plate with a minute pair of oval pleopods, each ending in a 

 seta. 



Five male specimens were obtained. Length of the 

 sjiecimeus 19-21 mm. from front of head to the end of pleon ; 

 of first antennae 15-17-5 mm.; of second gnathopod 10"5- 

 12 mm. 



LocaUfy. — D'Entrecasteaux Channel, Tasmania, 2-11 

 fathoms. On a Hydroid (Sertularia o;perctolata, Jjinnaeus) . 



