| OCR Text |
Show 1903.J MARINE FAUNA OF ZANZIBAR. 143 there comes first a region of about forty segments bearing small gills of three or four filaments; these gills at about the sixtieth segment rapidly enlarge and consist of four or five filaments, though they never become long enough to meet over the back. So far as Grube's and Baird's descriptions go, the last two species correspond with M. januarii and M. parishi. Indeed the comb-seta? of the latter form a distinct point of similarity between it and M. furcellata. But the descriptions published of these two forms are so exceedingly meagre that certainty is impossible, so that in preference to the risk of giving two worms a distribution from East Tropical America to East Africa, I have described my forms de novo. Genus LYSIDICE. LYSIDICE COLLARIS Ehr., Grube. This species, though never abundant, occurred at most of my collecting-places, viz., two specimens from Wasin Harbour (one from between tide-marks, the other from a depth of 10 fathoms), two smaller ones from 3 fathoms in Chuaka Bay, and three, smaller still, from the shore near Zanzibar Town. Discrepancies of some importance occur between the descriptions of the species already published by Grube (Red Sea and Philippine collections), Marenzeller (Japan), and Gravier (Red Sea). My own collection shows that variations of features, usually considered diagnostic, occur in specimens from the same locality. The name ' collaris' obviously refers to the white ring found near the anterior end of the living animal. As the colour disappears from specimens which have been a few years in spirit (it is already becoming faint in m y own after the lapse of one year), it has not yet been described. The ground-colour is a bright yellow-brown, best developed anteriorly and gradually dying out at about the tenth setigerous segment. Posteriorly the body is nearly colourless, unless sexual products, which are pink, give it that colour. In one of m y specimens (and presumably in that collected by Ehrenberg) this pigmentation is interrupted by numerous small white dots, and is omitted altogether from segments three and four, forming the above-mentioned white collar. In the remaining specimens, one of which is of equal size to this, the coloration is perfectly uniform. The form of the body is in life, as after preservation, flat below and strongly arched above throughout its length. The insertion of the tentacles is not noticed by former authors except Gravier, and in this respect, as in others, none of my specimens agree with his description. The tentacles, though a little narrowed at their bases, have no distinct basal joint, and though they in some cases arise from nearly the same level, yet the origin of the middle one is always in front of the origin of the other two, thus reversing the usual arrangement. The prostomium itself is rather longer than in Gravier's figure. |
