54 Tanaidacea and Marine Isopoda from Juan Fernandez. 



By 



Ake nordenstam. 



With Plate 20 and 12 text figures. 



Through Professor Carl Skottsberg the task has been confided to me 

 of describing the Tanaidacea and marine Isopoda collected during his expedition 

 (1916— 17) off the Juan Fernandez-Islands by Dr. K. BACKSTROM. For this 

 kindness I express to Professor SKOTTSBERG my best thanks. I also wish to 

 thank my friend Dr. N. Odhner at the Natural History Museum (Riksmuseum) 

 in Stockholm for having facilitated my work in various ways. 



The material consists of 10 species, of which not less than 7 are new. 

 Of only one of the new species, Lanocira hirsuta, there are plenty of indi- 

 viduals. 4 new species, Aega bicavata and 3 species oi Paranthiira, must be 

 described from only one specimen each, and of the remaining 2 new spe- 

 cies, Tanais (Anatanais) marmoratiis and lineatus, there are unfortunately no 

 full grown individuals. I regret that owing to these circumstances the descrip- 

 tions are necessarily imcomplete. 



For the drawings and photographs illustrating this paper I am indebted 

 to Mr. S. Ekblom and Mr. C. Svedi^n. 



Order TANAIDACEA. 



Fam. Tanaidae. 



Genus Tanais Audouin and Milne Edwards 1829. 



Subgenus Anatanais n. subgen. 



The large number of species belonging to Tanais are clearly to be 

 divided into two groups, one Tanais s.s. with 5, the other with 6 free abdom- 

 inal segments. Both Stebbing (1905) and (NiERSTRASZ) 191 3 regard this diffe- 

 rence as of almost generic value. As later investigations have failed to discover 

 transitional forms, I completely agree with this view, and I propose for the 

 forms with 6 free abdominal segments the new subgeneric name of Anatanais. 



In 1914 Vanhoffen gave a list of species of Tanais described up to 

 that year. From his group of Tanais with 6 free abdominal segments T. 

 Stanfordi Rich. (cf. RICHARDSON 1901) should, however, be removed. In the 



34 — 29232' rA« Nai. Hist, of Juan Fernandez and Easter Isl. Vol. III. 



