634 



OLIGOCHAETA 



glands are limited to a single pair in the thirteenth segment, a difference from all 

 other members of the subfamily. Urobenus is like Pontoscolex, and Trichochaeta, 

 in having a series of posteriorly situated glands ; a remarkable point in its structure 

 is the existence of a pair of caeca in the same segment as that in which similar 

 caeca occur in the not nearly allied genus Perichaeta, viz. the twenty-sixth. This 

 last fact leads me to include MICHAELSEN'S Anteus papillifer in the genus Urobenus; 

 in this species the setae are wanting upon the first few segments of the body ; the 

 only other members of the subfamily Geoscolicidae in which the same cephalization 

 occurs is in my genus Onychochaeta, in Tykonus and (occasionally) in Rhinodrilus ; 

 these genera so far approach the subfamily Microchaetidae, where the absence of 

 setae on the first few segments is not unfrequently met with. In view of the fact 

 that the setae of the first few segments of the body are absent in worms, not by 

 any means nearly related to the Geoscolicidae, e. g. the Naidomorpha, too much 

 stress perhaps cannot be laid upon the resemblance. Ilyogenia might reasonably be 

 regarded as a somewhat degenerate ally of Rhinodrilus. 



The following tabular statement of the principal differences between the species 

 of 'Anteus' described by MICHAELSEN (10); his genus Tykonus and BENHAM'S (3) 



Urobenus, may precede a discussion as to the systematic position of this species 

 referred to. 



The most marked character common to several of these species is the absence of 

 setae on some of the anterior segments. This is most marked in Tykonus, and the 

 fact that in that worm the ventral setae do not commence until the thirteenth 

 segment, while the dorsal do not appear until the twenty-sixth segment is the chief 

 reason for distinguishing the genus, which ' in other respects stands near to the genus 

 Anteus.' But we find that the same deficiency of setae anteriorly distinguishes 



