M. R. Leuckart on the Young States of some Annelides. 259 3. Rhynchonella psittacea was moderately abundant in the extreme north, from Tromsoe to the North Cape, in a living state, in 70 to 150 fathoms water. Dead valves were found at Hammerfest in mud. I found Rhynchonella very difficult to examine, the animal being extremely timid and closing its valves on the slightest movement. The coiled arms are extended, so that the cirri when unbent come as far as the margin of Rhynchonella psittacea. the shell. I have frequently seen this spe-cies with its valves open, but it never protruded its arms. 4. Crania anomala, Miill. sp., was met with between Drontheim and Tromsoe, at-tached to stones, shells, &c., in 40 to 150 fathoms water; the cirri are protruded, but not the arms, beyond the mar-gin of the shell. The valve opens by moving upon the straight side as on a hinge, without sliding the valve. Crania anomala, Miill. sp. XXIV. — On the Young States of some Annelides, By R. Leuckart *. [With a Plate.] In his copious " Observations on the Anatomy and Development of some Invertebrate Marine Animals,^^ Busch has figured (pi. 8. figs. 1-4) the larva of an Annelide of unknown origin, which is particularly remarkable in many respects, and especially from its possession of strong spines and fringes of cilia upon the in-dividual segments. In the spring of 1853 I not unfrequently took similar larvae from the surface of the sea near Nice and Villa Franca. The stage of development in which they occurred agreed pretty well with that observed by Busch, at least in most of the specimens : younger larvse were never found, but some occurred which had proceeded a little further, and these proved their increased development especially by the partial or even complete loss of the above-mentioned spines. When the tem-porary nature of this peculiar apparatus of bristles was esta-blished, it was tolerably easy, by the consideration of the other * Translated by W. S. Dallas, F.L.S., from Wiegmann's Archiv, 1855, p. 63.
BioStor
