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.
Shell spiral, turbinate, dextral, imperforate, spirally ridged or double-keeled and transversely wrinkled; spire prominent, its nucleus sinistral; aperture ovate, canaliculated 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 canal; 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 analogy of the shell with Spirialis. (Mus. Brit. & Geol.)
The only known species, C. huxleyi (dedicated to Mr. Huxley, Assistant 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 canal. The entire lip is marginated by the thickened and reflected peristome. I believe this curious floating shell 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.