OCR Text |
Show 1 9 0 5 .] SPECIES OF WORM FROM TIIE RED SEA. 561 tins septum is not quite so strongly developed as those wliicli lie in front. The last hearts lie in segment xiii. The nephridia are obvious in segment xv. The spermatheccp, which open in line with the male pores, i. e. with seta b of Michaelsen's scheme*, have a single diverticulum of about half the length of the pouch itself. Their pores are situated between segments vii./viii. and viii./ix. The spermiducal glands, like those of some, but not every, species of the genus, possess a distinct duct separable from the glandular and also tubular region by a constriction and by its nacreous appearance due to the strong muscular coat. The glandular part is fully six times as long as the muscular duct. The duct in the fully mature is curved into a horseshoe-shape. It is of uniform thickness thougbout, and does not increase in diameter towards the external pore. For the purposes of an easier comparison with other species I append a definition of this new Pontodrilus, which I propose to name after Mr. Crossland. Pontodrilus crosslandi, sp. n. (Text-fig. 78.) Length about 100 mm. Prostomium ejncheilous (g~g). Setce paired rather distant ; distance a-b less than c-d. Clitellum x i i i - xviii. Male pores (on xviii.) and spermatheccd pores (vii./viii., viii.fix.) in line with seta b. Pap Hire paired on inter segmental areas xiii./xiv., xiv./xv. Last thickened inter segmented septum xiii./xiv. Last hearts in xiii. Spermathecce with single diverticulum half the length of the pouch. Spermiducal glands with distinct muscular duct.-Hab. Shores of KJhor Dongola,, Red Sea. In view of the cutting of the Suez Canal and the alleged and consequent migration of the Mediterranean fauna eastwards and of eastern additions to the same f , it is important to note that the species Pontodrilus crosslandi is by no means a variant of, or most nearly related to, the Mediterranean P. littoralis. It comes nearest, as I am inclined to think, to P. laccadivensis and P. matsushimensis var. chathamiana by reason of its anteclitellian papillfe, unknown in other species. It lacks the papillfe following the male pores, which are so general in Pontodrilus. To emphasise the likenesses and also the differences between P. crosslandi and P. laccadivensis I add a figure of the latter (text-fig. 79, p. 560) for purposes of comparison. This species has not yet been figured, though its essential characters have been described +. * Oligochaeta, in ‘ Das Thierreich,' 10 Lief. (Berlin, 1900). f E. A. Smith in P. Z. S. 1891, p. 396. x Beddard in ‘ The Fauna and Geography of the Maldive and Laccadive Archipelagoes,' vol. iv. pt. iv. p. 374. |