PILSBRY: non-marine MOLLUSCA of PATAGONIA. 515 



Chilinidas : Cliiliiia teJutekJia, C. puck ha, C. parcJmppii. 

 Lymnaeidae : Lymiicea viator, Plaiiorbis peregrimis, P. anatiniis. 

 Ancylidas : Aiicyliis conceiitrkus bonarknsis. 

 Amnicolidae : Littoridina parchappii, L. australis. 

 Sphaeriidcie : Not reported, but doubtless present. 

 Unionidae : Dipiodoii patago)iicus. 

 M u t e 1 i d as : Atiodontiks piiekhana. 



B. Rio Chnbiit Fauna. 

 Unknown. 



C. Rio Santa Cruz Fauna} 



Chilinidae: Chili na strebeli, C. sniithi, C. fu/gurata, C. f. oligoptyx, C. f. 



livida, C. f. andicoki, C. f. hatcheri, C. campylaxis, C. nionticola pilula, 



C. iebruni, C. perrieri. 

 Lymnaeidae : Lymncsa viator, L. diaphana, L. d. inekgans, L. patagonica 



riochicoensis, L. andeana. 

 Amnicolidae : Littoridina hatcheri, L. sinipkx, L. sublineata. 

 Sphasriidae : Musculium patagonicwn, Pisidium magellanicum, P. pata- 



gonicum, P. observationis. 



D. Magellanic, Fuegian and Falkland Faunas} 



Chilinidae: Cliilina patagonica, C. anioena, C. fuegiensis, C. nionticola, C. 



fusca, C. nervosa, C. falklandica. 

 Lymnaeidae : Lymncsa diaphana, L. patagonica, L. pictonica, L. brunneo- 



Jiavida. 

 Sphasriidae : Pisidium magellanicum. 



These several faunas may be roughly compared with the life-zones of 

 North America. The La Platan zone is equivalent to the Austral, the Rio 

 Negro fauna to the Transition, and the remainder of the Patagonian zone 

 to the Boreal zone of the northern continent. 



The distinctness of the Patagonian faunas A, C, D may be attributed 

 to three main factors : (i) Climate, which imposes limits on the north 

 or south distribution of species. (2) Absence of streams flowing north or 

 south, and the consequent isolation of the river systems, favoring the evo- 



' Known only from the collections of Mr. J. B. Hatcher. 



-From the researches of Captain Kinj^, Dr. Coppinger, the U. S. Exploring Expedition, the 

 French E.xpedition to Cape Horn, Dr. Michaelson and others. 



