Volume Ii Part 45 (2/2)

clathratulus of the seas of the Northern Hemisphere. It is dedicated to the author of the Voyage of the Fly.

New Genus--MACGILLIVRAYIA, Forbes.

Sh.e.l.l spiral, dextral, globular, thin, corneous, transparent (in the only known species smooth or marked by obscure lines of growth) imperforate; spire not produced (with a sinistral nucleus ?). Aperture oblong, entire, angulated below; peristome incomplete, thin, even-edged.

Operculum semicircular, h.o.r.n.y, thin, composed of concentric layers with faint traces of a spiral structure at the centro-lateral nucleus, which is on the columellar side; from it there runs a strait rib or process continued nearly to the outer margin, and indicated externally by a depression or groove.

Animal ample, provided with four very long and rather broad linear rugose (or ciliated ?) tentacula; mantle produced into a long siphon; foot very large, expanded, truncate in front, bearing the operculum near its posterior extremity, but not accompanied by filamentous processes or lobes. A float. (Mus. Brit. and Geol.)

This very remarkable mollusk was taken in the towing net off Cape Byron, on the east coast of Australia, in lat.i.tude 28 degrees 40 minutes South, fifteen miles from the sh.o.r.e. It was floating and was apparently gregarious. Mr. Macgillivray states that it is furnished with a float in the manner of Ianthina. The largest specimens measure rather less than two lines in diameter. The sh.e.l.l is of a yellow horn colour (as is also the operculum) thin and transparent. It bears a striking resemblance to our much more minute Jeffreysia opalina. The four tentacula and the form of the very peculiar operculum also seem to indicate considerable affinity with the genus Jeffreysia of Alder, and an examination of the remains of the tongue extracted from a dried specimen showed an arrangement and form of the lingual denticles very closely resembling that exhibited by Jeffreysia. On the other hand, the very distinct and long siphonal tube delineated in Mr. Macgillivray's drawing, taken when the animal was alive, would seem to refer this genus to some family probably near to Cancellaridae. It is certainly entirely distinct in every respect from any known Gasteropod. It is a form of very great interest to the geologist, for in it we see the nearest representation of certain palaeozoic (especially Lower Silurian) univalves. .h.i.therto referred to Littorina, but which, judging from their a.s.sociates and the indications afforded by the strata in which they are found, were a.s.suredly either inhabitants of deep water or floaters in a great ocean like the Pacific.

I have dedicated this most interesting creature to my friend Mr.

Macgillivray, its discoverer, whose researches have been productive of so much new and valuable contributions to all departments of zoological science.

I have named the species M. pelagica. Tab. 3 fig. 8. a, b, c, d. (Mus.

Brit. and Geol.)

New Genus--CHELETROPIS, Forbes.

Sh.e.l.l spiral, turbinate, dextral, imperforate, spirally ridged or double-keeled and transversely wrinkled; spire prominent, its nucleus sinistral; aperture ovate, ca.n.a.liculated below, its outer margin furnished with two claw-like lobes, the one central and formed by a prolongation of the margin between the keels of the body whorl, the other smaUer and nearer the ca.n.a.l; peristome thickened, reflexed, forming a conspicuous margin.

Operculum none ?

Animal unknown, but certainly floating, and probably pteropodous. This I infer from its habits, and from the a.n.a.logy of the sh.e.l.l with Spirialis.

(Mus. Brit. & Geol.)

The only known species, C. huxleyi (dedicated to Mr. Huxley, a.s.sistant Surgeon of the Rattlesnake, and now eminent for the admirable anatomical researches among marine invertebrata which he conducted during the voyage) is very minute, being not more than the 1/24th of an inch in diameter. It is translucent and of a brownish-white hue. Its aspect is that of a Turbo in miniature. The whorls are tumid, the spire prominent; the body whorl is belted by two prominent keels, one of which is continued on the whorls of the spire: between, above, and below these keels are transverse membranous raised ridges, which in the central division of the body whorl are curved forwards. This curvature corresponds with the projection of the curious incurved claw-like lobe that proceeds from thc central portion of the lower lip. Towards the base of the aperture is a second and similar but smaller lobe, below which is the short but broad and well-marked ca.n.a.l. The entire lip is marginated by the thickened and reflected peristome. I believe this curious floating sh.e.l.l will throw some light on the true nature and habits of several palaeozoic types. It was taken in the towing net, gregarious, in the sea off Cape Howe, the south-east corner of Australia. Tab. 3 fig. 9. a, b.

CONTENTS OF PLATES OF NEW Sh.e.l.lS.

Tab. 2.

Fig. 1. Helix brumeriensis.

Fig. 2. Helix franklandiensis.

Fig. 3. Helix inconspicua.

Fig. 4. Helix iuloides.

Fig. 5. Helix divisa.

Fig. 6. Helix yulei.

Fig. 7. Helix dunkiensis.

Fig. 8. Helix louisiadensis.

Fig. 9. Balea australis.

Fig. 10. Pupina grandis.

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