ORTMANN: CRUSTACEA OF SOUTHERN PATAGONIA. 663 



We see at once that, while the prevailing features of the southern 

 Patagonian marine fauna are made up chiefly by peculiar species, another 

 large part of the fauna shows unmistakable affinities to other Antarctic 

 countries. Looking more closely upon the peculiar types (group 4), we 

 are able to state the following particulars with regard to their relationship 

 to other parts of the world. 



The genera Elminhis, Edotia, and Eiirypodius do not find any closer 

 relations elsewhere. Exospharojua and Serolis are distinctly Antarctic 

 types, while the affinities oi Rociuela and Mitnida are more or less cosmopoli- 

 tan. There remain only the two Lithodidce and Hypopeltariitm. The Litlio- 

 didc2 apparently are to be classed with those forms which possess a kind 

 of bipolar distribution, but where the two polar areas are connected along 

 the western coast of America. This has been called by the present 

 writer " meridional distribution," ' and such cases are not considered to 

 belong to " bipolarity " in the original sense. Hypopeltariitm, which is 

 represented in European waters by Atelecyclus, might be taken for a case of 

 bipolarity, if it were not for the fact that a species of this genus lately has 

 been discovered in the West Indian region.- This renders it impossible 

 to regard this case [oi Hypopeltariimi and Atekcyclus) as one of bipolarity. 



Examining the Antarctic types (group 3), we find that none of them 

 can be regarded as a representative of any characteristic Arctic form, 

 although among the five isopods the generic affinities need further investi- 

 gation. This much is known, that all five of them are hardly represented 

 in any part outside of the Antarctic regions. The same is true of Halicar- 

 chius, while Afitmda, as has been stated above, is cosmopolitan. 



Thus, among the forms discussed here, the bulk is to be regarded as 

 peculiar to this region, representing a local Magcllanian fauna. A large 

 part of this fauna exhibits characteristic Antarctic affinities, pointing to a 

 former closer connection of the different parts (South America, New Zea- 

 land, Australia, Kerguelen, etc.). The remaining small number represent 

 either immigrants from the north, along the western coast of America, or 

 more or less cosmopolitan types. 



The Magcllanian fauna, according to this material — and this is no 

 doubt a fair representation of the more abundant forms of it — is descended 



'See Ortmann in Zool. Jalirb. Syst., v. 9, 1896, p. 584, and Bronns Klass. and Ordn. d. 

 Thierrcichs, v. 5, Crust., 1900, p. 1279; see also Bouvier, 1896. 



-II. dextruin Rathbun in: Bull. Labor. Univ. Iowa, 1898, p. 277 (from Yucatan). 



