70 MARINE EARTHWORMS. [CH. I 



present our knowledge of their anatomy is not sufficient 

 to decide the point definitely. In America besides the 

 genus Microscolex already described we have the bulk of 

 the species of the semi-aquatic genus Ocnerodrilus, also 

 found in Tropical Africa, and a species or two of the genus 

 Pontodrilus, which is like no other earthworms except the 

 ubiquitous genus Pontoscolex in living among the debris of 

 sea-weed on the sea-shore. The other species of this genus 

 live respectively in the Aru Islands, on the shores of the 

 Mediterranean, and the North Sea, affording an example 

 of the frequently wide range of forms whose habitat is a 

 narrow area. This family of earthworms is one that is so 

 difficult to classify in a satisfactory manner that it is not 

 wise to draw any conclusions from its range except to 

 point out the similarity between South America and New 

 Zealand. 



