VON JHERING : ON SOUTH AMERICAN MYTILIDiE. 97 



*2Iytilus exustus, Linn. : Bahia to the West Indies. 



* ,, Domingensis, Lam. : Uruguay to the West Indies. 

 „ Darwinianus, Orb. : Rio Negro to Ilio de Janeiro. 



,, Podriguezi, Orb. : Patagonia to Kio Grande do Sul. 

 ,, oralis, Lam. : Magellan Straits to St. Cruz; Chili. 

 ^Modiolus tulipa. Lam. : St. Catharina to the West Indies. 



* ,, Brasiliensis, Chem. : S Paulo to Guiana; Panama; California. 



* ,, pictus, Lam. : North Brazil to Antilles. 

 *Lithophaga nigra, Orb. : Kio de Janeiro to Carolina. 



* ,, hi sulcata, Orb. : St. Catharina to Carolina. 



* ,, Patagonica, Orb. : Magellan Straits to Bio Negro. 

 Modiolaria Chenuana, Orb. : " Brazil." 



* ,, opifex, Say : St. Catharina to Carolina. 



* ,, viator, Orb. : Patagonia to the West Indies. 



1 * Crenella divaricata, Orb.: Argentina to Florida ; California. 



Of these twenty species eleven are Antillean, that extend to 



Northern Brazil, Rio de Janeiro, St. Catharina, etc., or even to 



Patagonia (Rio Negro), but no single species is common to the 



Antillean and the Magellanic districts. This is not astonishing, since 



the Brazilian coast fauna is essentially a depauperate Antillean one. 



In many families the Brazilian species are also all common to the 



: West Indies. All the species of Area, Cardium, etc., occur both on 



r the Guiana coast and in the Antillean Ocean. The special feature 



; of interest about the Mytilidse is that a large number of the species 



: are not found in the West Indies at all. 



1 Among these are the Magellanic forms, Mijtilus edulis, If. Magellanieus, 

 [ II. oralis, and Lithophdga Patagonica. The relationship of the last- 

 ' mentioned species is not evident. My specimens have two somewhat 

 | pronounced lines running down from the umbones, that indicate 

 : affinities with L. limlcata, Orb. If these lines were to completely 

 ■' disappear, the shell would be indistinguishable from L. cristata. 

 i It seems, therefore, that L. Patagonica is a variety of one of the 

 Antillean species. 



The three species of Mytilus, on the contrary, are Antarctic forms, 



: distributed from the Magellan Straits on both sides of Patagonia, 



" They are species of wide distribution, that may have attained their 



present distribution in times when the Antarctic lands were more 



1 connected than they are to-day. Mytilus edulis is also an Arctic 



species, and apparently occurs along the western coast of America. 



This wovdd suggest that the species may have migrated along the 



west coast of America to the Magellan Straits, and then wandered 



upwards on the Atlantic side to southern Brazil ; but of all the 



j species which seem to have reached the Magellanic province by 



southward migration, such as Monoceras concholepas, etc, not one has 



wandered to eastern Patagonia ; and the occurrence of 3f. edulis 



cannot well be explained on different grounds from the rest. It must 



be remembered that 31. edulis and 3f. Magellanieus occur not only on 



the Patagonian coast, but also at Kerguelen, New Zealand, etc. There 



is not sufficient palseontological material available at present to enable 



