TANAIDACEA AND MARINE ISOPODA FROM JUAN FERNANDEZ 529 



of the distal setae on the carpus are visible, 2 of them being hidden by the 

 propodus. 



Pleopods normal. 



The uropods consist of 8 joints (subadult male, length 5 mm) and 6 joints 

 (immature specimen, length 2.3 mm). 



Remarks. Tanais inarmoraUis very much resembles the previously de- 

 scribed species 7". litoralis Vanhofifen and T. gracilis Heller, of which two 

 species VaneiOffen (1914) says that immature specimens cannot with certainty 

 be distinguished from each other. 



The new species shares with T. litoralis Vanh. the possession of very 

 strong chelipeds and, like that species, is of a bluish-grey colour. It differs, 

 however in the greater number of joints in the uropods in specimens of about 

 equal size. 



From the figures and description of T. gracilis Heller made by Heller 

 (1865) and by Stebbing (1905), T. marmoraius only differs in its anteriorly 

 narrower carapax, a character which in T. marmoraUis is distinct in the small 

 specimen also. The difference could be explained as being of a secondary 

 sexual nature, but such a sexual difference is not known in the genus. 



From T. gracilis, as described by Vanhoffen (191 4), T. marnioratus 

 differs very much more in its very broad chelipeds. One cannot, however, be 

 quite sure that T. gracilis of Vanhoffen is the same species as the original 

 one described by Heller. Indeed Tattersall (1921) has pointed out that 

 T. gracilis Vanhoffen cannot at present be separated from T. Ohlini Stebbing. 



That, on the other hand, T. gracilis is identical with T. spongicola Bar- 

 nard is the opinion of VanhOffen (1914) and of Barnard (1925), a view 

 which is very probable, at least as regards the specimens seen by Vanhoffen. 



If this is correct T. Ohlini is probably a distinct species, in view of the 

 differences in the mouth-parts between this species and T. spongicola. 



Tanais (Anatajtais) lineatus n. sp. — PI. 20, figs. 2, 3; text figs. 3, 4. 



25 immature specimens of a length varying between 2.5 and 4 mm. 12 

 females, 13 males. 



Loc. Juan Fernandez: Masatierra, 30—40 m, sand with calcareous algae. 



The two sexes are separated by their different shapes of body. 



The females (PI. 20, fig. 3) are subcylindrical. The ventral side is slightly 

 vaulted and their height is about ^j^ or more of their width. The thoracic 

 segments have the lateral margins strongly convex, and the 5th, 6th and 7th 

 are longer than they are broad. 



The males (PI. 20, fig. 2) are broader and generally a little shorter. They 

 are ventrally flat and their height is about Yg of their width. The lateral mar- 

 gins of the thoracic segments are straighter, and the 5th, 6th and 7th thoracic 

 segments are broader than they are long. 



Description. 



Body about 8 times as long as it is broad (in male only about 5 — 6 times). 



