PEOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 179 



ORDINARY MEETING. 



Feiday, 13th I^ovembek, 1896. 



Dr. H. "Woodward, F.R.S., etc., Vice-President, in the Chair. 



Professor G. Gilson was elected a Member of the Society. 

 The following papers were read : — 



1. " Descriptions of new species of Mollusca belonging to the genera 

 Lotorium, Pecten, and Cardium, from the collection of M. Thomas, 

 of Brest." By G. B. Sowerby, P.L.S., etc. 



2. "The Polyjjlacophora of South Anstralia." By W. T. Bednall. 



3. " Abstract account of the second and third parts of M. Bernard's 

 paper on the Morphology of the Hinge in Pelecypoda." By B. B. 

 "Woodward, F.L.S., etc. 



Mr. J. Green and Mr. J. H. Gardiner exhibited a series of skiagraphs 

 of Molkisca taken by the E.ontgen-rays, which were commented on by 

 Mr. B. B. Woodward. 



The examples shown were obtained by means of a Crookes 

 tube (focus pattern), actuated by a powerful induction coil giving 

 8 in. sparks, and the exposures raried from a few minutes for a large 

 Clausilia to a little more than an hour for Nautilus pompilius. 



In all the Gastropods the columella was distinctly shown up to the 

 very apex, with all twists and plaits on it, the latter being perfectly 

 marked, even through the shelly pillar, as in Voluta ; the clausium was 

 indicated in Clausilia, as well as the various folds, and the notches 

 in the margins of the plates of Cryptoplax were rendered visible through 

 the substance of the girdle. A group of shells taken with fragments 

 of calcite and aragonite made it clear, by the opacity of the minerals, 

 even when thinner than the shells and far more transparent to ordinary 

 light, that the passage of the X-rays through the shells must be due 

 to the presence of the organic matter in their substance. 



A close inspection of the skiagraphs revealed the fact that they 

 faithfully reflected the different relative thicknesses of the shell 

 substance interposed between the tube and the photographic plate. 

 Hence the external ornamentation is reproduced, and even, as in the case 

 of the Nautilus (selected for reproduction here, PI. XV), the lines of 

 growth ; whilst in this instance, too, the varying degrees of solidity 

 of the siphuncle, and the point of attachment of the shell-muscle, are 

 well brought out. 



Mr. G. B. Sowerby exhibited specimens of Pinna saccata, L., from 

 South Afi'ica ; also a specimen of Voluta Junonia, Chemn., with its 

 periostracum ; and the types of the new species described in his paper. 



On behalf of Mr. W. T. Bednall, specimens were exhibited in 

 illustration of his paper. 



Mr. E. R. Sykes exhibited various Polyplacophora from South 

 Australia. 



