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Show 1890.] WORMS OF THE GENUS PERICH.ETA. 65 PERICHCETA 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 great 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 setce 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 Perichceta 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 19th, 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 biseriatis (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 separating segments 7 and 8 is thickened and then there is a considerable 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 mesentery, and the 11th from the 12th; these two are much thicker than the mesentery between segments 7 and 8, especially the first of the two. The spermatheca 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 diverticulum. 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 specimens, 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 |