144 



PROCEEDINGS OF THE MALACOIOGICAL SOCIETY. 



with from three to five pustulose ribs, the outer ones being the more 

 prominent, small granules studding the spaces 

 between the ribs. Sutural plates roimded ; sinus 

 wide, somewhat inclined to convexity. Interior 

 white. Posterior valve very indistinctly radiated, 

 but iiTegularly concentrically granulated towards 

 the margin and everywhere studded with smaller 

 granules. Umbo antero-central, the slope behind 

 it scarcely concave. The anterior valve has 1 1 , 

 the median 1, and the posterior 11 slits. Girdle 

 densely covered with very small flattened, im- 

 bricating, striated scales, becoming smaller to- 

 wards the outer edge. Length 38, breadth 

 12 mm. 



Bah. — Sultana Bay, Yorke Peninsula, at which 

 locality only a few specimens have been obtained. 



In reference to this shell Mr. Pilsbry writes 

 that it is allied to /. cariosus in the sculpture of 

 the central areas, but has the girdle of the typical 

 Ischnochiton Pilsbryi, Ischnochitons. 

 n.sp. 



7. Ischnochiton ustulatus (Eeevc). 



Chiton ustulatus, Peeve: Conch. Icon., sp. 102; Pilsbry, Man. Conch., 

 ser. I, vol. xiv, p. 96, pi. xxiv, figs. 100, 1-4, 11, 12. 



An elongate oval shell of a scorched brown hue, except upon the 

 dorsal ridge of all the valves except the anterior one. On the summit 

 of the last seven valves the dominant colour gives place to creamy 

 white with longitudinal splashes of burnt brown. The surface of the 

 valves is apparently smooth, but by the aid of a lens is seen to be 

 minutely reticulated. The lateral areas are but slightly raised, and 

 both they and the tenninal valves are very indistinctly radiately and 

 concentrically striated. The girdle is pale yellow, and the scales on 

 it so minute as not to be discernible without the aid of the microscope. 

 Interiorly the shell is tinged with puiple, paling to bright pink at the 

 junction of the valves, a characteristic that is constant and serves well 

 as a means of identification. Old specimens are very much eroded 

 on the dorsal ridge. Length 45, breadth 16 mm. Large specimen, 

 1. 67 X 21 mm. 



Hah. — Many stations in St. Vincent's Gulf, under blocks of lime- 

 stone, at low-water mark. Fine specimens east and west sides of 

 Southern Yorke Peninsula. 



Not included in Mr. Angas' List of South Australian Mollusca, but 

 recorded by him from New South Wales, where it does not appear 

 to occur. I have received specimens of /. divergens under this name. 

 The excessively small girdle-scales are diagnostic. In life this Chiton 

 is a very conspicuous object, the deep dark-brown shell standing out 

 in strong: contrast to the brilliant orange -coloured girdle surrounding it. 



