AUSTBAtrAlT MALACOSTEACA. 303 



Tribe ANISOPODA. 



Body sub- cylindrical or dorso-ventrally compressed. The 

 thoracic legs consisting of an anterior series of four and a 

 posterior of three pairs. Segments of the abdomen, except the 

 last, usually short, sometimes more or less coalescent. Abdo- 

 minal appendages of the first fiye pairs f oliaceous and branchial ; 

 those of the last pair operculiform, lamellate, styliform or obso- 

 lete. Terminal segment usually large, destitute of appendages. 



Sub-Tribe Aecttjeidea. 



Posterior pair of abdominal appendages operculiform, covering 

 the branchial laminae. 



Family ABOTUBIDJE. 



Sub- Family Arctwinm. 



Abdominal opercula closely appressed to the ventral surface 

 of the abdomen. 



G-enus Abctitkus, Latr. 



Body sub-cylindrical. Segments of the thorax usually more 

 or less tuberculated, sometimes sub-equal, sometimes with the 

 fourth very long. External antennae large, with a stout peduncle 

 and a flagellum of few or many articuli. 



522. Arcturus longicornis. A.M. 



Arcturus longicornis, Haswell, 1. c, Vol. vi., p. 194. 



None of the segments of the thorax greatly elongated. Head 

 broader than long, longer than the first segment of the thorax ; 

 frontal border deeply concave. A pair of pointed spinous tubercles 

 on the head, on each segment of the thorax, and on each of the 

 first two segments of the abdomen. Terminal segment sub-acute, 

 with a pair of rounded tubercles near its apex. Internal antennse 

 longer than the head ; first segment of the peduncle short and 

 thick, second and third segments sub-equal. Outer antennse 

 with the peduncle equal in length to the head and thorax — the 

 fifth joint much longer than all the rest together. Length, 

 exclusive of antennae, more than two inches. 



