ZooL— Vol. II.] RISEN— OLIGOCHMTA. 229 



External Characters. 



Somites. — The prostomium (fig. 84) is very small and 

 causes only a small indentation in somite I, which is the 

 narrowest, being about one-third the width of II. The 

 somites following increase slightly in width up to somite VI 

 and VII, both' of which are of equal size, and about twice 

 as wide as I. Somites VIII to XII gradually decrease in 

 size towards the clitellum, which commences in the center 

 of XII and continues to the center of XIX. The somites 

 posterior to the clitellum are much narrower but more dis- 

 tinctly three-ringed. Somite I is narrowest on the ventral 

 side. 



Dorsal-pores. — First pore III/IV. The first very distinct 

 pore, viewed exteriorly, is V/VI. 



Setce. — The setae are strictly paired and ventral, not 

 reaching the lateral line. The couples are nearly equidis- 

 tant from each other, except in the somites where a deltoid 

 arrangement is found, similar to that which is seen in some 

 species of Microscolex (Deltania). The distance a-a in- 

 creases from about somite XXVIII to XVII, in which is the 

 male pore; and from XVII the distance increases forwards 

 to somite XI, then decreases towards VIII and VII, the 

 spermathecal somites. From VII forwards there is first a 

 slight increase, then a narrowing towards I. 



All the setae are slightly sigmoid, with four or more sHght 

 notches or spines near the apex. There are two bunches of 

 penial set£e in XVII, at each male pore. The projecting 

 part of the setae is either slightly curved or perfectly 

 straight, tapering to a fine point, which is bent in a right 

 angle and furnished with a knob. The outline is strongly 

 wavy, showing about seven sharp knees on either side, but 

 with no other ornamentation. The smaller seta has the 

 knees less prominent and the bent apex longer, and the 

 knob fully as large as that of the larger seta. The third seta 

 appears to be undeveloped. In one sac this seta was very 

 strongly curved. 



