Report on the zoological collections made in the Indo-Pacific Ocean ...

M0LLU8CA. 83115. Chiton (Macandrellus) costatus. (Plate VI. fig. F.)Acaiitliochites costatus, II. Adams *^- Angas, Froc. Zoo/. Soc. 1864,p. 194 ; Anffas, I. c. 1807, p. 224.Macaudrellus costatus, Z>«//, i)"«//. U.S. Nat. Mas. i. p. 81, fig. 40(dentition).JIab. Port Jackson {Angas and Coppinger).The single specimen before me, preserved in spirit, shows thegirdle to be of a pale buff colour, thick, fleshy, the outer marginbeing delicately ciliated with a minute fringe of white spicules.The tufts of spicules arc seven in number along each side, and foursurrounding the front valve. The middle of the central valves isoccupied by a raised, transversely substriated flattened ridge, on eachside of which the surface is granulated or rather squamose, thescales being flat, imbricating, rather large, and disposed in ratherregular series. The lateral areas are well defined by a raised keel.The front valve has five radiating costte, and apparently the samenumber of slits in the thin lamina of insertion, of which the threecentral are quite distinct, and the two outer ones only feebly indicated.The single notch on each side the intermediate valves isalso very slight. The posterior valve has a raised, somewhat excentricand pointed mucro, from which six more or less distinctradiating ridges descend to the margin, beneath which the laminaof insertion is scalloped by a similar number of notches.116. Chiton (Acanthochiton) ashestoides. (Plate VI. fig. G.)Shell small, greyish brown, with a pale line on each side themiddle of the central valves, slightly converging behind, leaving adark wedge-shaped space between them. Surface covered with acoarsish granulation, the granules being somewhat flattened, andthose at the vertex of the central valves rather smaller than therest. The lateral areas are not defined in these valves ; the posteriorcurved margins are produced in the middle, at times almost forminga right angle ; their insertion-plates are large, thin, produced anteriorly,with a very slight notch quite close to the hinder margin oneach side ; the sinus between them in front is deep and arcuate.The first valve has a straighter posterior margin than the succeedingones, and a semicircular outline in front ; the lamina of insertionis rather deep, thin, feebly striated exteriorly, and interruptedby five very small subequidistant notches. The last valve is conspicuouslysmall, transversely subovate, depressed-conical, with anearly central mucro ; insertion- plate very large, laterally produced,with only two notches behind. Interior of the valves bluish.Mantle very minutely spinulose, bearing very conspicuous compacttufts of silky spicules along the sides, not at all unlike in their fibroustexture that of asbestos. Length 15 millim., width of the broadestcentral valve 5|.Hah. Flinders Island, Bass's Straits {Joseph MiUlgdn); PortMolle, Queensland [Coppint/cr).g2