MELANGES BIOLOGIQUES 



TIRÉS DU 



BULLETIN DE L'ACADÉMIE IMPÉRIALE DES SCIENCES DE ST.- PÉTERSBOURG. 



TOME XIII 



Crustacea caspia. Contributions to the knowledge of the carcinological 

 Fauna of the Caspian Sea, by G. 0. Sars, Prof, of Zoology at the 

 University of Christiania, Norway. (Lu le 15 septembre 1893). 



Part II. 



CUMACE J±- 



With 12 autographic plates. 



INTRODUCTION. 



In my former paper on Caspian Crustacea (Mysidse), I adverted to the 

 interesting fact that, in addition to Mysidœ and Amphipoda, also the exclusive 

 marine order Gumacea has turned out, by the investigations of Mr. War- 

 pachowsky, to be well represented in the Caspian Sea. It is now my pur- 

 pose, in the present paper, to treat of the several forms of the latter order, 

 which have hitherto come under my inspection. As will be shown, it is by 

 no means, as should, indeed, have been expected, a scanty and depaupe- 

 rated Cumacean fauna that inhabits the Caspian Sea. On the contrary, the 

 results hitherto gained would seem to prove, that the peculiar physical and 

 biological conditions, prevailing in that isolated basin, must have had a 

 most beneficial influence on the development and thriving of these interesting 

 Crustacea; for the species are rather numerous, and in some places appear 

 with a great abundance of specimens. Moreover, several of the forms attain 

 a rather large size, as compared with their allies in the Oceans, and are 

 only surpassed by some of the giant arctic species of the genus Biastylis. As 

 regards outward appearance, the species exhibit rather conspicuous differences, 

 being partly rather clumsy, partly extremely slender, and some of them 

 acquire, moreover, a most peculiar aspect by the strange development of 

 dorsal crests on the free segments of the mesosome. To judge from these 

 very conspicuous differences in the outer habitus, one would at first be 

 disposed to believe, that they belonged to several distinct genera. This, 

 however, is not the case. For anatomical examination has indeed shown 

 them all to belong to one and the same genus, viz., Pseudocuma G. 0. Sars. 



Bulletin N. S. IV (XXXVI) p. 297. 33 



