42 



DISCOVERY REPORTS 



Mastigopus I (Figs. 33 a, c, 34). Length 37 mm. Rostrum 0-85 mm. 



Rostrum denticulate, with minute spine at base. Supraorbital, hepatic and anterior 

 lateral spines present, much reduced. Dorsal organ small. Abdomen with conspicuous 

 lateral spines on somites 1-5, dorsal spines reduced to minute points on somites i and 2, 

 but rather long on somites 3-6. Telson with anterior lateral spine and small terminal 

 fork ; two or four setae within the fork. 



Eye more than one-fifth length of body, the width of the eyeball more than half length 

 of eye. Antennule with first segment of peduncle much the longest, the third slightly 

 shorter than the second. Antennal flagellum longer than body. Mandibular palp of good 



Fig. 33. S. corniculum A. a, Mastigopus i moulted from Acanthosoma ; 

 b, telson of Acanthosoma ; c, telson of Mastigopus. 



size but unsegmented. Maxillipede 3 and leg 3 nearly the same length. Legs 2 and 3 

 chelate. Legs with long twisted vestiges of exopods. Pleopods long; pleopods 3-5 with 

 setose endopods, the fifth the longest; pleopod 2 with rudimentary, non-setose endopod. 

 Uropods slender, about 1 1 times as long as wide ; setose margin nearly, or quite, twice 

 the bare part. 



There is some variation in the number of setae on the telson and in degree of 

 development of the pleopods. Also the vestiges of the exopods of the legs may be much 

 reduced. 



Colour. Red in thorax as in Acanthosoma. The legs may be colourless or with red 

 distally. Later stages become more and more red, especially on the legs (Fig. 35). 



Mastigopus 2 was obtained by moult from stage i. Stage 2 differs very little from 



