IN THE ' BIOLOGIA CENTRALI-AMERICANA.' 547 



American families, and there is good evidence that the main 

 . distribution of freshwater fishes changed but httle during the 

 Tertiary. The Eocene Friscacara, from the Green River Shales 

 of Wyoming, is, in my opinion, not one of the Oichlidse ; 

 it belongs to the North- American family Centrarchidse, and is 

 closely related to the modern Eupomotis. 



When we get to know something about Cretaceous freshwater 

 fishes new light may be thrown on the problem. But for the 

 present the hypothesis that South America and Africa were 

 formerly one continent is the one that offers the most reason- 

 able explanation of the relationship between their freshwater 

 fishes. 



Mr. R. I. PooocK, F.R.S., F.L.S., F.Z.S., remarked that 

 evidence for the former existence of a ti-opical or southern 

 Atlantic connection between South America and Africa was 

 supplied by the following, amongst other, genera of Arthro- 

 poda : — 



Pjhoxotracheata. — Peripatus is confined to tropical West 

 Africa and tropical Central and South America and tlie Antilles. 

 Opisthopatus is found only in Chili and Cape Colony. 



Diplopoda. — The Spirostreptid genus Orihoporus, which is of 

 wide distribution in tropical America, is very closely related to 

 tropical African, but not to tropical Asiatic, millipedes. 



Chilopoda. — Parotostigmus occurs in tropical America and 

 Africa, but not in tropical Asia. Scolopendra (s.s.) is mainly 

 tropical and Central American, but in the Old World it has been 

 recorded from the Cameroons, the Canary Islands, Arabia, and 

 Sokotra. 



ScoRPiONES. — Of the three tropical American genera of the 

 Scoi'pionidae Ojyisthacanthus has its nearest ally m the tropical 

 and South- African Ofisihocenirus ; and Diplocentrus and Oiclios 

 are closely related to the Arabian and Syrian JS'ebo, the three 

 together constituting the well-marked subfamily Diplocentrinse. 



Arane^. — The Sicariidte (s.s.) range in America from Chili to 

 Costa Rica, and are only found elsewhere in the world in South 

 Africa. Of the three genera of Caponiidaj JVops and Caponina 

 are tropical American, Caponia South Afiican. 



In the case of the above-mentioned Arthropods no reason can 

 be assigned for their extermination elsewhere in the tropics, if 

 they are the only extant representatives of genera formerly 

 widely distributed in the Northern Hemisphere. 



In the case of the Mammalia the evidence rests mainly upon 

 the present distribution of the three following orders :— - 



SiRENiA. — The Manatees {Trichechus) are restricted to the 

 rivers and estuaries debouching into the Atlantic on the African 

 or eastern side and on the American or western side. These 

 animals do not venture out to sea, and no extinct representatives 

 of the genus appear to be known from European or North- 



