SCHIZOPOD FROM TASMANIA. 287 



tlie appearance of an Ampliij)Ocl, and (2) the external lamellate brancliite of the thoracic 

 appendages. 



The cephalic segment is short and is produced into a triangular subacute rostrum 

 (PI. XXIV. fig. 2) ; the front margin, which is slightly hollowed out for the eye-sockets, 

 is entire and rounded ; the sides are not produced far downward, but leave the tumid 

 basal joint of the mandibles exposed. 



The eight thoracic and the six abdominal somites are distinctly articulated one to 

 another, but there is much room for overlapping between them, so that a considerable 

 power of flexion on the dorsal line is provided. In many specimens the posterior margin 

 has its overlapi)ing portion distinctly marked out from the rest of the segmeat by its 

 much paler colour. 



The first thoracic segment is only about half as long as the cephalon ; its lateral 

 portion, which extends further down than the sides of the preceding segment, is separated 

 ofi" l)y an oblique line into a distinct cpimeron, which is widest anteriorly. The other 

 thoracic segments are rather short, so that the thorax and cephalon together only equal 

 in length the whole of the abdominal portion. The sides of all the segments are rounded 

 and do not extend far down ; there is no trace of epimeral marking, but the margins are 

 thicker and more strongly chitinized than the remainder of the segment. Viewed 

 externally, the lateral margins of the thoracic segments are nearly hidden by the branchiae, 

 which project almost to the bases of the second antennae, and by the plumose exopodites 

 of the 2nd to 6th pairs of pera;opoda, which are produced upward and backward on 

 the sides of the body. 



The colour of these animals is a brownish grey, ajoproximating closely to the sides and 

 bottom of the pool in which they were found. The iutegument is very thin and some- 

 what tough, thinner indeed than that of any other free-swimming Crustacean with which 

 I am acquainted. This is no douljt due in part to the semi-subterranean abode in which 

 the animals occur. The external layer of the integument is transparent, and underneath 

 it are cells containing the pigment to whicli the colour is due. There is no calcareous 

 matter in the integument, neither nitric nor glacial acetic acid producing any trace of 

 effervescence, or indeed appearing to alter it in any way. Strong nitric acid alters 

 the pigment to a yellowish colour and rapidly dissolves it. The pigment-cells are 

 somewhat hexagonal in form, and can be removed in a thin layer, presenting a tesselated 

 appearance. 



Appendages. 



The eye-peduncles are short and stout, and are directed obliquely outward ; they reach 

 beyond the extremity of the basal joint of the second antennae, Imt not so far as the 

 extremity of the basal joint of the first pair. Each peduncle is 1-jointed, cylindrical in 

 form, and very slightly enlarged toward the extremity; its length is about twice its 

 diameter. The ocelli, which are very numerous, occupy about the upper third of the 

 stalk ; just below them, particularly on the outer side of the peduncle, are a very few 

 short stiff hairs. 



Anterior antennce (PI. XXIV figs. 3 and 4). — These organs are normally formed. The 



38* 



