ENCHYTR^ID^ *73 



than in that species. Two large sperm-sacs extending through several 



somites anterior to XI. In shape these sacs resemble those of E. 



saxicola. 



Genus Michaelsena Ude (part). 



Definition. — Setae straight, more or less absent in majority of the 

 somites. Head-pore between prostomium and somite I. No dorsal 

 pores. Esophagus gradually merging into the intestine. Dorsal ves- 

 sel rises posterior to clitellum, and is without cardiac gland. No pep- 

 tonephridia. Testes solid. Nephridia as in Enchytrcsus. Penial 

 papillae without interior muscular strands. No penial bulbs. 



To the definition given originally by Ude I have added the charac- 

 teristics of the penial bulb, and modified that referring to the setze. It 

 is to my mind evident that if we are to recognize the genus Michael- 

 sena we must make the definition wide enough to include both Mich- 

 aelsen's species, Enchytrccus monochcetus .^ and my new species, 

 Michaelsena j)aucispina. These species differ but slightly from M. 

 subtilis Ude, the differences referring only to the number of missing 

 setae. In M. faucispina the setae are entirely absent on the anterior 

 three somites, and in all the other anterior somites only two ventral 

 setEe are found in each somite. In some of the posterior somites there 

 are four setae in each somite. In Enchytrceus monochcetus a further 

 reduction has taken place, as there are no setse in the anterior five so- 

 mites. Then follow other somites with only ventral set£E, while the 

 majority of somites seem to possess four rows of single setae. In Af. 

 subtilis another step in the reduction has been taken, and we find in 

 this species only ventral setae in somite IV, V and VI. In all the other 

 somites the set£e are absent. I cannot see how we could very well in- 

 clude one of the above species in the genus and exclude the others. 

 So far as known there are no characteristics of sufficient importance to 

 separate these three species in different genera. 



SYNOPSIS OF SPECIES. 



1. Michaelsena subtilis Ude. SetJe found only in somites IV, V and VI, and 



here only two pairs corresponding to the ventral fascicles. Size 5 to 6 mm. 



2. M. monochivta (Michaelsen). The anterior four or five somites without any 



setae. The foUow^ing few somites possess only single ventral setse, while 

 all the other somites possess four single seta, each setae corresponding to 

 single fascicle. Length 7 mm., width .25 mm. 



3. M. faucispina sp. nov. Somites I, II and III without setae. All other 



anterior somites with two ventral setae, each seta corresponding to a fasci- 

 cle. The posterior somites with four setae each, each seta corresponding to 

 a fascicle. Length 7 mm., width .2 mm. 



It may be noted that all the three species seem to be marine forms, 

 occurring along the seashore among seaweeds. 



