OCR Text |
Show 1903.] FROM EAST AFRICA AND ZANZIBAR. 257 having been distinguished by any difference or intensity of colour. It exactly resembled a piece of the racemose seaweed (Caider pci) on which it was found. The length of the alcoholic specimens is 2 centim.; the extreme breadth of the back with cerata 8 millim., and of the foot 2'3 millim. The rhinophores are long and distinctly canaliculate. There are no oral tentacles, but two lobes over the mouth. Behind the rhinophores are two very distinct black eyes. The cerata are club-shaped as in Galvina, of varying size, the largest inside. On each side of the back are four clumps of about nine cerata each, and there is a thick bunch on the tail, which, however, projects a considerable distance behind the last cerata. Dow'n the centre of the back is a broad bare space, in the anterior portion of which is the very large, elongated (not oval) pericardial prominence. In front of this and fused with it is the vent, a large and conspicuous tube. The foot is rounded in front. I dissected one specimen, but was unable to obtain a clear view of either the central nervous system or the reproductive organs. The latter, as usual in this family, were extremely complicated, both the prostate and albumen-gland appealing to be extensively ramified. The verge was armed with a small spine. The hepatic diverticula in the cerata, being colourless, were not easy to distinguish, but appear not to be much ramified and to resemble the figure of those in Ercolania siottii in Trinchese, pi. ix. fig. 2. The mouth-parts, buccal muscles, radula, &c. are of the usual ascoglossan type. The teeth are not unlike those of Ercolania viridis (v. Bergh, I. c. pi. xii. figs. 3 & 4), but the dorsal surface is a simple curve and does not show any depression. The upper portion of the radula contains 6 teeth, the lower 27, the last members being arranged in a spiral like that depicted in Trinchese's plate of E. siottii (pi. x A. fig. 1), from which it may be concluded that the individual is young. As the specimen presents all the characters of the genus Ercolania, I describe it under that name, but I feel very doubtful if the genus is valid. The only characters which differentiate it from Stiliger, viz. that the rhinophores are canaliculate and the pericardial prominence elongate and not oval, are surely very slight. Vayssi&re (I. c. p. 122) referred to the genus a species (funerea) with entire rhinophores, which is probably in any case a Stiliger. The animal is not likely to be specifically identical with E. viridis Bergh, for the coloration is not really the same, the size is much larger, and the shape of the teeth somewhat different. 17* |