LARVAE OF SERGESTES 



27 



apical fork very slender, parallel, or even bending slightly inwards, not reaching end of 

 uropods. Each arm with two outer spines and with or without one inner spine near apex. 



Eye about one-seventh length of body, its length nearly twice the diameter of the 

 eyeball, which is nearly round. Antennal scale widening towards the end, about five 

 times as long as wide ; flagellum about half length of body. Mandibular palp rudi- 

 mentary, but with apical setae. Legs with vestiges of exopods. Pleopods very long, 

 with rudiment of endopod on 2-5. Exopod of uropod with bare part a little longer 

 than setose (i : o-8) and six times as long as wide. 



The stout, broad body is characteristic of this species, and is retained in all stages. 

 The dorsal spines of abdominal somites 4 and 5 remain up to a length of about 8 mm. 

 The mandibular palp is still unsegmented in stage 2. At a length of about 7 mm. it is 



Fig. 19. S. crassus. Mastigopus telson. a, 4-2 mm.; b, 4-85 mm.; c, 4-68 mm.; 

 (f, 5-45 mm.; e, 6-95 mm.;/, 14mm.; », 15 mm. 



large, two-segmented, and setose. The transformation of the telson is shown in Fig. 19. 

 The largest Mastigopus is about 10 mm., and there is an immature phase, according to 

 Hansen, up to about 20 mm., during which the petasma is formed. 



Colour. Red in thorax, but abdomen colourless. Red patches in antennae and all 

 limbs, and in exopod of uropods. 



Sergestes robustus Smith 



Lo Bianco, 1903, p. 182, PI. vii, fig. 9, Acanthosoma 2. 

 Hansen, 1922, pp. 114, 117, Mastigopus and Acanthosoma. 

 Illig, 1927, fig. 62, Acanthosoma (as S. arcticus). 

 Cecchini, 19286, p. 34, Mastigopus. 



Material. Larvae of this species were taken but rarely at Bermuda, and only over 

 very deep water, at depths of about 250 m. Moults were obtained of first to second 

 Acanthosoma and of Acanthosoma to Mastigopus, but the identity of the Elaphocaris 

 was not proved by moult. 



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