OCR Text |
Show 328 MR. OTBIL CROSSLAND ON THE [Feb. 16, first region, which narrows slightly to its posterior end, and the rest of the body retains this slightly decreased breadth to near the anus. The figure of the worm (PL XXII. fig. 10) gives these proportions and illustrates the differences between the two parts of the body. As here shown, the change is quite sudden at the point given. The prostomium (PL XXII. fig. 10) is nearly as broad as the buccal segment and slightly notched anteriorly in the usual way. The tentacles are smooth, short and thick, the longest projecting but very little beyond the edge of the prostomium. The eyes are large and densely black, of a half-moon shape, or slightly crescentic from some points of view. The tentacular cirri are remarkably small and slender. The upper jaw-plates are of the usual type, the only noticeable features being the bluntness of the teeth and the length of the supports at the base of the great dental plates. As would be expected from the small size of the worm, the plates are delicate and of a light brown colour, but calcareous matter is not visible. T«xt-fig. 65. Upper and lower jaw-plates of Nicidion gracilis. X 60. There are two black crescentic paragnaths, one on either side above and exterior to the crescent plates. The lower jaws can scarcely be called plates, they are so delicate and flexible. The shapes of all these parts are shown in text-fig. 65. |