THE GENERA OF NEMERTEANS. 227 



36. Tetixistemma dorsalis Abildgaard. 

 Synon. Tetrastemma fuscum Oersted. 



» variegatum Leuckart. 



» marmoratum Claparède. 



Is present at Naples in several varieties : witli a dorsal 

 median line , marbled on the back , of a uniform dark 

 colour, etc. I have nothing to add to the descriptions 

 of previous authors. 



37, Tetrastemma jiavidum Ehrenberg. 

 Synon. Polia sanguirubra Quatref. 



» obscura v. Beneden. 

 Tetrastemma varicolor Mac Intosh. 



Only a few specimens of this species, so well characte- 

 rized by the considerable distance between the anterior and 

 posterior pair of eyes, have come under examination. 



38. Tetrastemma candidum (0. F. Mull.) Oersted. 

 Synon. Polia quadrioculata Quatref. 



Tetrastemma varicolor Oersted (pro p.). 

 » algae Leuck. 



The Naples representative of this species is rather com- 

 mon and generally of a bright green colour. Other varieties 

 are more yellowish. For further details I refer to Mac 

 Intosh's description. 



39. Tetrastemma vermiculatum (Quatref.) Mac Int. 

 Synon. Polia vermiculata Quatref. 



The longitudinal dark bands between the two eyes on 

 each side render this species easily recognizable and by their 

 constancy prove the specific distinction to be well founded. 



Provisionally I aur in clined to regard as a variety of 

 this species, several specimens I received in which a white 



ISTotes from the Leyden M.iiseuxa, 



