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Show 56 ZOOLOGICAL COLLECTIONS MADE DURING [Jan. 4, CYCLOSTOMATA. IDMONEA MILNEANA, d'Orbigny. Ldmonea milneana, d'Orbigny, Voy. Amer. me'rid. p. 20, pi. ix. figs. 17-21; Busk, Cat. Mar. Polyz. Brit. Mus. pt. iii. p. 12, pi. xi. Tubidipora transversa, Lamarck?, Anim. s. Vert. (l)ii. p. 162. Ldmonea transversa, M.-Edwards?, Ann. Sci. Nat. (2) ix. p. 218, pi. ix. fig. 3. This is certainly the species described and figured by Busk. His description requires emendation by the substitution of "thin" for "thick" as a character of the margin of the cells, and bv the insertion of " a long backwardly directed spine on the back of the main aud sometimes of the smaller branches." One such spine, and perhaps the trace of another, broken off, occurs on the specimens already in the Museum. In the two relatively smaller specimens in this collection they are more abundant; in one case the two primary divisions of the stem each bears one ; and of their branches, one of the one and both of the other bear them. They are strong; and the maximum length appears to be about 3 millims. As pointed out by Haswell (Proc. Linn. Soc. N . S. Wales, iv. p. 351) in a specimen assigned by him with doubt to this species, the " dots " of Busk's description are certainly raised. But the truth lies between the two ; for they are also perforated in their centre in the original British- Museum specimen and the Magellan one. The alternating character of the lateral series of cells, which is very slightly marked in the Patagonian specimens alluded to (from which the account in the British-Museum Catalogue was in part written), and which is almost lost sight of in d'Orbigny's account, is here strongly marked. The longitudinal striation and the concentric lines on the back are also well marked here. Hab. T o m Bay, near Madre-de-Dios Islands, S.W. Chili, 0-30 fathoms, embedded in base of a horny Sponge, partially overgrown by Lepralia monoceros and a creeping calcareous Sponge. Obs. This may possibly prove, as Busk says, to be I. transversa, Milne-Edwards ; but the habit of growth as figured by M.-Edwards, and the locality (Mediterranean) as given by Lamarck, are against the idea. Smitt, in his 'Floridan Bryozoa,' remarks on this species that the typical number of cells in the transverse rows is three, varying to two or even one in the lower parts. In the present specimens the number never falls below three, and is as often four as three, if not oftener. He has also observed "radiciform pillars" at the back of the branches of one of his specimens; but there their ends were expanded into clasping processes and attached it to a foreign body, whereas in the Chilian specimen they end simply. DIASTOPORA PATINA, Lamarck. Tubidipora patina, Lamarck, Anim. s. Vert. (2) ii. p. 244. Diastopora patina, Smitt. (Efv. K. Vetens. Ak. Forh, 1866, p. 397, pi. viii. figs. 13-15. |