DISCOVERY REPORTS 



Acanthosoma 2 (Fig. 12 b, c). Length 4-8 mm. Rostrum 1-4 mm. 



Rostrum with large basal spine. Supraorbital spine much shorter than eye. Hepatic, 

 two pairs of lateral and posterior dorsal spines about equal. Dorsal organ small. Dorsal 

 spines of abdominal somites i and 2 shorter than those of somites 3-5 ; lateral spines 



Fig. 12. S. arcticus. a, Elaphocaris 2; b, Acanthosoma 2; c, telson; d, e, telson of 

 Mastigopus 5 and 7 mm.;/, antennal scale of Acanthosoma i. 



decreasing backwards, those of somite 5 small. Basal part of telson more than twice as 

 long as wide, with small lateral spines; arms parallel, about three-quarters length of 

 basal part, with two inner and two outer spines. 



Eye about one-quarter length of body, the eyeball nearly round and less than one- 

 third length of eye. There is a very small anterior papilla. Antennal scale very slender, 

 with long apical spine ; flagellum 5 mm. Mandibular palp present, unsegmented. 



