| OCR Text |
Show 1904.] FROM EAST AFRICA AND ZANZIBAR. 93 than usual in the other species, but with a very thick rhachis and lpmnate. The rhinophores are large and exserted, each bearing about 35 perfoliations. The rims of the pockets are very slightly raise . The oial tentacles are two hard black ridges, curved downwards and sideways. The foot is narrow and grooved in front. . The buccal mass was extracted, but the animal was not further dissected in order to preserve the specimen. There is no labial armature. The formula of the radula is 13 x 3 + 1.1.1 + 3. The teeth closely resemble those of JV. gratiosa, the chief difference being that the anterior margin of the wide median tooth (fig. 3 c) is indistinctly bilobed, the right half being always a little higher than the left. Ihe first lateral (fig. 3 cl) is large, rather irregular in shape, and with a double hook at the apex. This form is closely allied to JV. gratiosa, and were the latter found in the Indo-Pacific region, I should be inclined to regard them as varieties of one species. But JV. gratiosa is recorded from the West Coast of Mexico*, which lies outside of the Indo- Pacific area; and it is therefore probable that the differences presented by the present animal are real and greater in living individuals. (a) It is not mentioned that JV. gratiosa is remarkably soft, (b) The present specimen shows no traces of ridges near the rhinophores or on the tail, (c) The coloration of JV. gratiosa is not dissimilar, but the pattern is spotted whereas here it is striped, (cl) The tentacles do not look as if they had ever been ear-shaped. (e) The anterior margin of the median tooth is indistinctly bilobed. M a r io n ia . [See especially Bergh, in Semper's Reisen, xv. p. 737, & xvii. p. 890.] All the Tritoniadse which I have collected in East Africa belong to this genus, unless the form described as Marionia sp. is regarded as sufficiently certain to constitute a new generic type. Marionia is distinguished from its near allies Tritonia and Gandiellci by the presence of a circle of horny plates or leaves in the stomach. The velum bears distinct processes, which are often ramified. The edge of the jaw has one or more rows of denticles, and the radula is moderately wide. The central tooth is broad and more or less distinctly tricuspid. The laterals are hamate, but the first one is larger and clumsier than the others. Provisionally I think it best to divide the forms here described among six species, but am by no means certain that they will all prove valid. When more matei'ial can be examined it will probably be found that the species of Marionia exhibit many varieties in form and colour and run one into another. It is also not impossible that the denticu- * In Bergli's ‘ System der Nudibr. Gasteropoden,' p. 1145, the locality is given as " mare indicum, Amboina," but this appears to be a slip. The animal is described by Bergh among the molluscs of Amboina, but is expressly said to come from Mexico. |
