1890.] WORMS OF THE GENUS PERICH^TA. 65 



Perich^ta forbesi, n. sp. 



I possess two specimens of this Perichceta, which were collected 

 by Mr. H. O. Forbes in New Guinea and given to me ; I have 

 $!;reat pleasure in associating the name of this new species with 

 Mr. Forbes. 



Both examples are of an almost exactly similar size. The length 

 is about 9 inches, the breadth nearly half an inch. The colour of 

 the spirit-preserved specimens is a dark greyish brown, darker 

 upon the clitellum. 



The prostomium is very small, and does not extend over a large 

 portion of the peristomial segment. 



The setcB form a continuous row round the middle of each 

 segment. 



The clitellum occupies the usual number of segments, i. e. 3 

 (segments 14-16) ; but the glandular tissue, instead of being, as is 

 usually the case, continued as far as the posterior boundary of 

 segment 16, appeared in both specimens to end at the setae of that 

 segment. 



As in Perichata affinis, setae are developed upon the ventral side 

 of the clitellum. 



The male generative pores occupy the usual position, i. e. upon the 

 18th segment. 



The 17th segment and the 1 9th, 20th, and 21st have each a pair 

 of genital papillae occupying a position corresponding to that of 

 the male pores, and situated like them just in front of the circle of 

 setae. The number and arrangement of the genital papillae of this 

 species serve to distinguish it from Perichceta biserialis {cf. Plate 

 IV. figs. 4, 5). 



The oviducal pore is single and median upon the 14th segment. 



Dorsal pores are present and commence between segments 12 

 and 13. 



The arrangement of the specially thickened mesenteries is very 

 distinctive of P. forbesi {cf. Plate IV. fig. 6). The mesentery sepa- 

 rating segments 7 and 8 is thickened and then there is a consider- 

 able interval consisting of three segments which are apparently 

 undivided by any mesenteries at all ; in this space lies the gizzard. 

 The 10th segment is separated from the 11th by a very thick 

 itiesentery, and the llth from the 12th; these two are much 

 thicker than the mesentery between segments 7 and 8, especially the 

 first of the two. 



The spermathecce present a character which is, so far as my 

 experience goes, unique among Earthworms, and that is their 

 marked asymmetry. 



In the 8th and 9th segments are a pair of these organs ; each is 

 a somewhat pear-shaped pouch with a single small sessile diverti- 

 culum. In the 8th segment, on the left-hand side of the body, was 

 an additional spermatheca placed close to the other one and of 

 exactly similar structure. This duplication occurred in both speci- 

 mens, but in the second specimen it affected the spermatheca of the 

 9th segment. It is of course possible that this structural peculiarity 



Proc. Zool. Soc— 1890, No. V. 5 



