DR. W. E. COLLIXGE ON A NEW SPECIES OF IDOTEA. 197 



Description of a new Species of Idotea (Isopoda) from the Sea of Marmora 

 and the Black Sea. By Walter E. Collinge, D.Sc, F.L.S., etc., 

 Research Fellow of the University of St. Andrews (The Gatty Murine 

 Laboratory, St. Andrews). 



(Plate 23.) 

 [R-ead 4th May, 1916.] 



In his interesting aceonnt of the Isopoda collected by the ' Thor ' on the 

 Danish Oceanographical Expedition, 1908-1910, to the Mediterranean and 

 adjacent seas *, Stephensen records from numerous Stations Idotea metallica, 

 Bc^c, remarking : "The determination of this species proved at first a matter 

 .of some difficulty, owing to the fact that all the specimens — with the excep- 

 tion of those from Sts. 208 and 341, which had exactly the same outline 

 as the figure given by Dollfus — were far narrower than they should be 

 according to the statements and illustrations published." 



For some time past I have felt convinced that there existed an allied 

 species which was being confused with L metallica. In connection with 

 other work on this family of Isopoda, I have had occasion to examine laroe 

 numbers of this latter species from our own coasts and from numerous 

 localities abroad, and I have been struck by the general uniformity that 

 prevailed in all the specimens. Thus it was practically impossible to find 

 the slightest difference in shape, size, or colour, in examples from Japan, 

 iNforth America, the Mediterranean and Adriatic Seas, and our own coasts. 



Miers t states that he had observ.ed "considerable variation in the degree 

 of promiu'^ice of the epimera [cox;d plates] and in the width of the thoracic 

 segments," and this only served to deepen the conviction that there existed 

 itwo closely allied, but distinct species. 



On comparing the figures of the appendages, etc., given by Stephensen 

 {op. cit. p. 13) with some recently made of I. metallica, I noted numerous 

 important differences, and so marked were these that I felt sure that he was 

 dealing with a species quite distinct from /. metallica. 



Dr. Stephensen has very kindly sent me for examination the whole of the 

 specimens collected by the ' Thor' at various Stations, and upon examination 

 it is at once evident that in addition to a few examples of /. metallica, Bosc, 

 from Stations 208 and 341, the remainder of the specimens are quite distinct 

 from that species. I am therefore describing the new species, with fio-ures 

 of the chief structural characters. 



* Vol. ii. D. i. 1915, pp. 1-53, 33 figs, 

 t Journ. Linn. Soc, Zcol. vol. x\i. (1881) p. 37. 

 LINN, JOURN. — zoology, VOL. XXXIII. 14 



