THK OLIGOCH.^TA OF NATAL AND ZULULAND. 407 



Acanthodrilus [Eodrilus] is archaic in character, and in 

 far-distant geological periods was spread presumably over all 

 the continents of the southern hemisphere as well as over the 

 neighbouring portions of the northern hemisphere, such as 

 Cameroon and Central America as far as Mexico. But this 

 wide region of distribution has been much restricted and 

 split up, and in recent times we only find the genus m scat- 

 tered and widely separated localities. One of these localities 

 is the southernmost corner of the African continent in the 

 vicinity of Cape Town. Here we find a small number of species 

 of Acanthodrilus, which give an archaic character to the 

 oligochajte fauna of the Cape region. In other parts of South 

 Africa, including Natal and Zuliiland, this archaic genus has 

 been exterminated and replaced by phyletically younger 

 oligoch^tes. In addition to the Cape Town residue we have 

 several different species of Acanthodrilus surviving in 

 Madagascar, and a single species in the Cameroous. 



In the other genus, Microscolex, the disti'ibution is quite 

 different. This genus is represented by a small number of 

 species in the southernmosn coastal districts of the Cape Pro- 

 vince. These extend eastwards as far as Port Elizabeth. 

 The genus Microscolex is phyletically younger than 

 Acanthodrilus, and has acquired the power of enduring- 

 salt-water, and thus it has the power of spreading widely 

 across the sea. It probably originated in the southern 

 corner of South America, and was distributed by means of the 

 west-wind drift over all the region of the subantarctic seas, 

 Patagonia, Falkland Islands, South Georgia, Crozet Islands 

 and Kers'uelen as far as the islands south of New Zealand.^ 

 In the course of distribution, which has probably occurred in 

 relatively recent times, the southernmost coast of Africa was 

 affected and became colonised with Microscolex. It Avould 

 appear that there has not been time for the genus to spread 

 further north, and so the oligocha3te fauna of Natal and Zulu- 



' Michaelsen. W., " Zur Kenntnis der Eodrilaceen nnd ilirer Ver- 

 lireitiuigsverhfiltnisse." " Zool. Jahrb. Syst.." xxx, p. 540 a. f., map p. 436. 



