J46 



THE GEOLOGIST. 



vided into equal parts, always enlarged at their extremity, 

 and narrowest at the base. Dorsal lobe generally the longest. 

 This group, which is one of the best characterized, is found 

 in the lower Jurassic formations, and the lower Cretaceous 

 rocks {A, fimbriatus and Jurensis from the Lias, and A, itke- 

 qualicostatus, subfimbriatus, Ophinurus^ Honnoratianus, recti- 

 costatus, lepidus, quadrisulcahis, striatisulcatus, strangularis, 

 Duvalianus, Juilleti, Matheroni, from the Neocomien). We 

 find that the greater number of the species belong to the 

 Neocomien, which is characterized by them. 



[To be continued.'] 



PROCEEBIBJGS OF SOCIETIES, 



GEOLOGICAL. SOCIETY OF LONDON. 



March 9th, 1842. — R. J. Murchison, Esq., President, in 

 the chair. The following papers were read, viz. : — 



1. — On the Salt Steppe, south of Orenburg , and on a remark- 

 able Freezing Cavern, by the President, 



This salt steppe differs from those between the Uralsk and 

 the Volga, or on the Siberian side of the Urals, in consisting, 

 not of a dead flat, but of wide undulations, and low ridges ; 

 it is nevertheless a true steppe, being devoid of trees, and 

 slightly irrigated. The surface is composed of gypseous 

 sands and marls, considered by Mr. Murchison to be of the 

 age of the Zeckstein, through which protrude the small pyra- 

 midal passes of rock salt, that led to the discovery of the 

 subjacent deposit. The salt is quarried to the south of the 

 village of lUatzkaya Zatcheta, and the excavations extend 

 about 300 paces in length, and 200 in breadth, the exposed 

 thickness of the mass being about 40 feet. The salt is 

 extremely pure, the only extraneous matter being a few 

 minute filaments of gypsum. At first sight the mass appears 



