33 



DISCOVERY REPORTS 



are greatly reduced. Stage 3 is probably represented in his figures 3 /, g, and we have 

 a very similar stage of g mm. in which the telson has not yet lost the form characteristic 

 of the Acanthosoma. The changes which take place in the telson are shown in Figs. 23, 24. 

 Colour as in the Acanthosoma. 



Fig. 24. S. robustus. Mastigopus telson. a, stage i ; b, stage 2 ; c, stage 4 ? 11 mm. moulted from form 

 like e\ d, stage 5 ? 12 mm.; e, stage 3, 6 mm.; /, stage 4, 10 mm.; g, h, moult and post-moult, 18 mm.; 

 i, moult to stage 4 (/). 



Sergestes prehensilis Bate 



Syn. S. gloriosus Stebbing 



(Gordon, 1935, J. Linn. Soc. xxxix, p. 314.) 

 lilig, 1927, fig. 125, Acanthosoma 2. 



Material. Discovery Station 282 (i°ii'S,5°38'E). One specimen of Acanthosoma 2. 



Description. Acanthosoma 2 (Fig. 25 a-c). Length 3-61 mm. Rostrum 1-42 mm. 



Carapace a little longer than wide. Supraorbital spine shorter than eye; four pairs 

 of marginal spines, of which the third is the longest ; dorsal spine present. Dorsal organ 

 small. Abdomen with dorsal spines on all somites, those of somites i and 2 not markedly 

 smaller than the rest. Lateral spines very long, that of somite 5 as long as somite 6. 

 Telson more than 2^ times as long as wide, with arms of distal fork slender, slightly 

 divergent, with three inner and two outer spines. Lateral spines of telson far in front 

 of fork. 



Eye less than one-sixth length of body; eyeball nearly round, its diameter about one- 

 third length of eye. Papilla present on stalk. Antennal scale slender, with long apical 

 spine ; flagellum twice as long as scale. Mandible with very small rudiment of palp. 



