460 



CRUSTACEA MALACOSTRACA. 



distinct. The eyes are pedunculate, the thoracic legs 

 flexed between the fifth and sixth segments and there are no oostegites 

 forming a brood pouch. 



Surviving in streams and freshwater pools at an elevation of 

 over 4,000 feet on the summit of Mount Wellington and elsewhere 

 in Tasmania, is a small crustacean measuring 1 to 1 J inches in 

 length, which appears in many of its characters to have retained 

 primitive features of the malacostracan stock. It was discovered 

 and described in 1892 by G. M. Thomson, and the very interesting 

 relations which it presents to other recent forms, and to palaeozoic 

 Crustacea have been set forth by Caiman. In shape it somewhat 

 resembles the Amphipod Gammarus, though it is less flattened 



laterally. 



There is no carapace, and the 

 head is divided off by a trans- 

 verse groove, which apparently 

 marks the front limit of the 

 thorax, though the forward 

 slant of the lateral parts of the 

 groove makes this conclusion 

 uncertain. The head shield 

 ends in a short rostrum in 

 front, on either side of which 

 are the stalked eyes. 



The 1st antenna has a 3-seg- 

 mented base and is biramous. 

 A statocyst is present in its 

 basal segment, as in the Deca- 

 pods. In the male the inner 



ramus is curved at the base and beset with hooks, recalling the 

 prehensile antennules of some Entomostraca. The 2nd antenna 

 has a small flattened scale-like exopodite. The mandible has a 

 large palp, but is without a lacinia mobilis. Of the two 

 maxillae the first resembles that of the Euphausiidae, but the 

 palp is vestigial. 



If the above-mentioned groove has been correctly interpreted 

 as marking the limit between head and thorax, Anaspides is 

 one of the few Malacostraca, in which the eight thoracic 

 segments remain distinct. Their appendages are biramous, 

 having an ambulatory endopodite (flexed between the 5th and 



FIG. 286. Anaspides tasmaniae (from Claus, 

 after Caiman). A' first antennae ; // 

 second thoracic segment ; Ep epipodites ; 

 T telson. 



