156 PROCEEDINGS OF TEE NATIONAL MUSEUM. vol.55. 



and erosion with periods of moist, tropical climate and partial sub- 

 mergence. The great land masses are chiefly in the northern hemi- 

 sphere and at times of maximum elevation are united into one 

 "irregular land mass with three great projections, South America, 

 Africa, and Australasia, radiating out from it into the southern 

 hemisphere." A lowering from present levels of 600 feet " would 

 isolate North America, South America, Asia, Africa, and Australia 

 as separate insular continents." 



One important principle of dispersal as announced by Matthew 

 (1915:180) is as follows: "Whatever agencies may be assigned as 

 the cause of evolution of a race, it should be at first most progres- 

 sive at its point of original dispersal, and it will continue this prog- 

 ress at that point in response to whatever stimulus originally caused 

 it and spread out in successive waves of migration, each wave a stage 

 higher than the previous one. At any one time, therefore, the most 

 advanced stages should be nearest the center of dispersal, the most 

 conservative stages farthest from it." 



According to these views we should expect to find the region of 

 origin and the center of dispersal of earthworms to be in the Holarc- 

 tic region and the more primitive types to be found in the more re- 

 mote areas as Australia, Africa, and South America ; while the more 

 modern, progressive groups are to be expected in Holarctic and ad- 

 jacent territory. A Gondwana continent would not be needed to 

 account for the present distribution of the Moniligastridae nor an 

 Antarctic continent to explain the distribution of Notiodrilus and 

 near relatives and to supply a center of origin and dispersal of earth- 

 worms in general, as is sometimes assumed. 



Michaelsen (1905:50-55) has expressed views concerning the dis- 

 tribution of the primitive kinds of earthworms which correspond in 

 some ways quite closely with the general principles of distribution 

 enunciated by Matthew. 



It seems somewhat surprising that Syngenodrilus which seems a 

 very primitive type of earthworm should be found closely associated 

 with such a highly specialized group as Polytoreutus^ and similarly 

 that Desmogaster should be found in a Pheretima region. 



Family MEGASCOLECIDAE. 



Polytoreutus of the subfamily Eudrilinae is a genus which in- 

 cludes about 30 described species, limited in their distribution to a 

 relatively small district in the east-central part of Africa. The two 

 species represented in the Chanler collection involve no change in 

 generic definition. 



POLYTOREUTUS CHALONERI, new species. 



Length, 10.9 cm. Diameter (maximum), 0.5 cm. Somites, 148. 

 Color (in alcohol), olive buff. Prostomium, prolobic. Setae (pos- 



