660 OLIGOCHAETA 



present to the number of three pairs only, as in the other species of the genus. 

 The spermathecae differ from those of the species P. corethrura in their number 

 (there are only two pairs instead of three) and in their form ; in the present species 

 the spermathecae consist of a reniform pouch communicating with the exterior by 

 & very long and narrow duct. The clitellum occupies segments xv-xxii, as in 

 P. corethrura; in other points the two species appear to agree. 



(3) Pontoscolex hawaiensis, NEW SPECIES. 



Definition. Length, \4imm.; diameter (at clitellum), ^.mm.; number of segments over 210. 

 Caudal zone at the end of second third of body. Setae paired at first, irret/ular 

 afterwards ; ornamented with, ridges on free extremity. Clitellum, XIII XXII. Dorsal 

 vessel double, the two vessels fusing at ihe septa. Hob. Hawaii, Mauna Loa (collected 

 by Mr. Perkins). 

 This species seems to be undoubtedly distinguishable from P. corethrurus. I 



have had the opportunity of examining eight or ten specimens all from the same 



locality. The caudal zone, as in P. corethrurus, appears to be constant in position ; 



this is shown by the following measurements of two individuals selected at random : 



A B 



Length of body in front of caudal zone ... 90 80 



behind ... 47 40 



The setae of this species have a much more marked ornamentation than in the 

 last, and their arrangement is a little different. On the clitellum, and for a few 

 segments behind it, the ventral setae are regularly paired, though each seta is 

 further away from its fellow than in front. On the other hand, the lateral pair of 

 setae are irregular on the clitellum; this, however, only applies to the outermost 

 seta ; seta three, to which corresponds the nephridiopore, has a fixed position. 



The dorsal vessel in front of and for a little while after it emerges from the last 

 thick septum is moderately thin ; it gradually becomes thicker and at the same time 

 moniliform ; the increased thickness is due to the fact that it is double ; its character 

 is like that of the dorsal vessel of Acanthodrilus novae-zelandiae : that is to say, it 

 is single where it traverses the septa. In the fourteenth and fifteenth segments the 

 dorsal vessel attains to its greatest bulk ; after this its calibre becomes suddenly 

 diminished; it retains, however, its double character. In one out of three specimens 

 dissected the dorsal vessel seemed to be single. The hearts are in xi and xii, and 

 appear to be only connected with the supra-intestinal vessel. I found the sperm-sacs, 



