98 TKOCEEDINGS OF THE MALACOLOGICAL SOCIETV. 



an exact idea to be formed on the relationships between the Arctic 

 and Antarctic representatives of If. edulis. It must also be observed 

 that If. Solis/anus is another analogous species, being represented in 

 Europe by If. minimus. Species of such wide and disconnected 

 distribution may have bad a much wider range in former times, and 

 subsequently have become extinct in the tropical regions. Still, the 

 geographical distribution of these species, as well as of If. chorus 

 and others, cannot be understood without recurring to the different 

 geographical conditions of the Antarctic region in Tertiary times. 



Turning to the other species of our list, Modiolaria Chenuana, like 

 Mytilus Hodriffuezi, seems to be restricted to the South Brazilian and 

 Argentine coast, while M. Darwinianus may be a variety of If. exustus. 

 There remain, however, two species having a highly interesting 

 distribution, If. strigatus and II. perna. As I have ah-eady said, the 

 singular II. falcaius, Orb., does not differ in form and coloration from 

 the Philippine species II. strigatus. On the other hand, II '. perna lias 

 a very restricted range on the Brazilian coast. There is no other 

 species of the subgenus Chloromya northward of Rio de Janeiro ; and 

 since the distribution of the subgenus is restricted to the Southern 

 Hemisphere, no species being proper to the Northern, and since the 

 same species, or a closely allied one, occurs in South Africa, we must 

 conclude that the Brazilian species came from the Antarctic region in 

 Tertiary times. A study of the Tertiary fauna of Patagonia proves 

 there was a warmer climate then. The pampean deposits of La Plata, 

 moreover, include species of Area, Purpura, Littorina, etc., which do 

 not now occur on the Argentine coast. I believe that the distribution 

 of If. strigatus can be similarly explained. 



All these facts impart a special interest to the study of these South 

 American Mytilidse, and it is, therefore, very desirable to obtain further 

 material in order to work out the complete synonymy and distribution 

 of these species, and their relationships with other allied forms in 

 different parts of the globe. 



