Geological Society. 513 



times exceed half an inch in diameter. The second genus is nearly allied 

 to Amia and Lepisosteus. The body is covered with hard quadrangular 

 scales, disposed in oblique rows. In all the species the peculiar forma- 

 tion of the tail, before alluded to, is the same. 



Along with the fish were found the remains of a Testudo, nearly al- 

 lied to Trionyx, and one specimen of a vegetable impression : but not 

 a single fossil shell oi zoophyte has yet been discovered in any part of 

 the county. It adds to the interest of this singular assemblage of organic 

 remains, that they all resemble the inhabitants of fresh-water. 



The formations in the lower region of East Ross also contain subor- 

 dinate beds of calcareo-bituminous schist; and though fossils are much 

 more rare than in Caithness, yet a few examples of fish-scales, and a 

 fragment of a Testudo resembling a Trionyx, have been found between 

 the North Sutor and Tarbet Ness. 



The authours remark that the great central deposit, containing the 

 ichthyolites, does not appear to be perfectly identical vnth any formation 

 hitherto described. It seems in some measure to occupy the place of the 

 coal formation. Many parts of it resemble grauwacke in raineralogical 

 character; and from its enormous developement, it can hardly be com- 

 pared with the copper-slate of Germany. None of the fish of Caithness 

 are identical with the fish of the copper-slate. 



June 6. — A letter to the President was read, from Gideon Mantell, Esq., 

 F.G.S., &c. enclosing a list of the fossils of the county of Sussex. 



This list, which is taken principally from specimens in the authour's 

 own collection, enumerates the fossils, first, of the alluvial and diluvial 

 deposits; and, successively, those of the London clay, the plastic clay, 

 chalk, chalk-marle, firestone, gault, Shanklin sand, and Hastings deposits, 

 including the Ashburnham beds. 



Subjoined is a comparative table ; one of the most remarkable features 

 of which, is the preponderance of the number of species in the marine 

 formations over those of the beds assumed to be of fresh- water origin, in 

 a ratio of not less than six to one ; the testaceous Mollusca forming two- 

 thirds of the whole, while in the fresh- water strata, the proportion is re- 

 versed. Thus the marine deposits contain upwards of two hundred and 

 forty species of shells, and the two frf.sh-water formations but twenty-two 



Vol. IV. M M 



