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Show 376 MR.R. B. WATSON ON MADEIRAN MOLLUSKS. [Mar. 18, Hab. Gorgulho, shore (very rare) ; Piedade (Canigal), 15-35 fathoms; Ponta de S. Lourengo, 25-4 5 fathoms ; Porto Santo, up to 50 fathoms; Santa Cruz, 10-15 fathoms; Machico, 10-15 fathoms ; Porta da Cruz, up to 50 fathoms ; Funchal Bay, up to 50 fathoms. This species is accepted as new by Mr. Gwyn Jeffreys and by the Baron Schwartz. From R. moniziana this species differs in that it is thinner, narrower, more pointed, more brilliant; the spiral threads do not present the same contrast with the interstices; these last are not so broad. Tbe mouth is rounded and on the same plane, not of the strange, triangular, oblique spoon-shape it has in that other. It certainly resembles the smooth and small variety of R. canariensis, in which the stain on the embryonic tip is often almost invisible; except in badly rubbed specimens of that species, however, some trace of that stain can be seen. Besides, this species as compared with R. canariensis is always narrower in proportion to length, is thinner, has the spiral threads more raised; and even when it has some trace of longitudinal ribs, these never show on the spiral threads. The labial rib, too, is by comparison quite insignificant. From R. aurantiaca it differs in that it has fewer, higher, and more distant threads, and no regular, raised, longitudinal ribs. A Sicilian Rissoa kindly sent me by the Marquis of Monterosato is quite certainly not this species. He has published the specific name above given. RISSOA CANARIENSIS, D'Orbigny. (Plate XXXV. fig. 12.) Not in M'Andrew's list. Hab. Gorgulho, shore; Santa Cruz, shore to 15 fathoms; Machico, shore to 15 fathoms ; Piedade (Canical), 15-35 fathoms ; Ponta de S. Lourengo, 25-45 fathoms ; Funchal Bay, up to 50 fathoms ; Porto da Cruz, up to 50 fathoms ; Porto Santo, up to 50 fathoms. Semifossil, Canigal beds. Teneriffe, shore (D'Orbigng) ; 40-60 fathoms (WAndrew). This species presents several variations of form ; but I am not struck by those, specially mentioned by Signor Manzoni, dependent on great differences in the proportions of the length and breadth of the shell. As in all the mollusks, some are larger than others, some are a little broader in proportion to length. The variety which departs most widely from the typical form is one uniform in colour, sometimes very light, sometimes dark chocolate, with the longitudinal ribs reduced to mere striae and much diffused and the spiral threads also much lowered; in this form it resembles a small variety of R. punctura, from which, however, it is easily distinguishable, above all, by the embryonic apex. I cannot but think that R. philippiana, Jeffreys, is only a striking and somewhat aberrant variety. It is identical with R. canariensis in the microscopic fretting of the whole surface, and especially in the microscopic markings of the embryonic whorl. R. canariensis differs from R. spreta in having no fosse on tbe |