48 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 17, 



tory of Gothland, where the preceding section terminates ; showing 

 how the same sandstone (i) which occupies the surface of the plateau at 

 Grbtlingbo on the N., is here brought down to the sea level ; thus proving 

 a general southerly inclination. The overlying calcareous strata (J, Jc, and 

 A*) are described in the memoir. 

 Fig. 13. General section from E. to W. across Scania. This is merely given to in- 

 dicate, as far 'as possible, the successive outcrops of Lower and Upper 

 Silurian rocks in a low obscure tract much covered with mud, rolled 

 blocks and gravel {bl). The Lower Silurian sandstone {a) is partially seen, 

 the alum schist {b) with its fine trilobites is copiously exposed, but the pre- 

 vailing Swedish and Russian Orthoceratite limestone with Cystidea is 

 no where seen, its place being taken by an occasional thin course of black 

 limestone subordinate to graptolite schists {d). The Upper Silurian 

 rocks are recognizable in grey limestones and shales (/, &c.) which are 

 surmounted by purple sandstones containing casts of Cypricardige and 

 other fossils apparently belonging to the uppermost zone of the Ludlow 

 rocks. The porphyry of Ofved Kloster is marked {p). 



June 17, 1846. 



George Aug. M. Dermott, Esq., and Thomas Macdougall Smith, 

 Esq., were elected Fellows of this Society. 



The following communications were read : — 



1. Description of a Fossil Chiton from the Silurian Rocks, with 

 remarks on the fossil species of the genus. By J. W. Salter, 

 Esq., F.G.S., of the Geological Survey of Great Britain. 



The discovery of a species of Chiton in beds of undoubted Silurian 

 age appears to be a fact sufficiently important to be brought under 

 the notice of the Geological Society, not only from the rarity of the 

 genus in a fossil state, but because it carries back to an earlier date 

 another of the many families we are in the habit of considering as 

 characteristic of later epochs. The shell I have now to describe 

 presents peculiarities distinguishing it both from recent species, and 

 also from those found in the carboniferous rocks. In introducing 

 the subject I propose to glance at the ordinary characters of the 

 family, for so this group must be considered, in order to show the 

 relation of the fossil with the living species. 



The Chiton is one of the lowest forms of Gasteropodous Mollusca, 

 and is considered by naturalists as closely allied to the genera, Patella 

 and Lottia, and as forming with them a distinct order of Mollusca 

 under the name of Cyclobranchia (Cuvier), distinguished by the ar- 

 rangement of the branchias. The Chitons have a double generative 

 system, terminating (according to Blainville and Rang) on either side 

 of the body. This is a very marked character, and one indicating 

 strongly the low position the group holds in the order to which it 

 belongs. The shell is of course the only part with which we have 

 to do (in treating of fossil species), and its variations are fortunately 



