124 TANAIS. 



last four species are described in detail in the second 

 series of the same work (vol. ii. p. 408). 



In a paper on the structure and relations of the genus 

 by Fritz Mliller (Archiv. f. Naturg. 1864, p. 1 — ) the 

 author is, however, induced to consider that T. Edwardsii 

 and Savignyi are the sexes of the same species, and 

 that T. curculio and Orstedii are in the same condition. 



From the various localities in which the different 

 species have been found, we presume that they were 

 taken at large by dredging, and consequently are not 

 parasitic in their habits. Van Beneden, however (who 

 has published some observations on the genus in the 

 fifth volume of the second series of the " Bulletin of the 

 Academic Royale de Belgique,^' as also in his "Re- 

 cherches sur la faune littorale de Belgique," Crust, p. 93, 

 pi. 166, where he has given a rude figure and details of 

 T. Dulongi), states that he obtained a male and five 

 females of that species from the carapace of a Chelonia 

 mydus, thrown upon the shore near Ostend, which would 

 indicate a carnivorous condition of life for that species. 



In a memoir on the relation which this genus holds 

 to the order of Isopoda,* Prof. Lilljeborg unites in 

 this genus not only Crossurus of Rathke, but also Para- 

 tanais and Leptochelia of Dana. By so doing he finds 

 himself compelled to commence by separating that 

 division of the genus which carry two branches to the 

 posterior pair of pleopoda from those that carry but 

 one. We tliink that it is more convenient, in our present 

 state of knowledge, to keep apart as much as possible 

 animals possessing a marked structural distinction. We 

 therefore retain in this work Dana's genus of Para- 



TANAIS. 



* Bidrag till Kiinneclomen om de inora Sverige och Norrige fore Kom- 

 mande crustaceer af Isopodernas underordniiig och Tanaideriias familj. 

 Af Wilhelm Lilljeborg. Upsala 1S64. 



