445 



\ 

 greater part are such as to point them out decidedly as peculiar to this 



stratum. 



In this stratum the fossil shells are exceedingly numerous: particularly 

 ammonite, nautilitte, terebratulita, gryphitte, mytulita, modiolita, spondylit*, 

 trigonitte, belemnit<e, and the large dona.r-formed bivalve mentioned p. 182. 

 In this stratum are also found fish of an unknown genus, with large square 

 Kales, PL XVIII, Fig. 9, and several species of Testudo, Lacerta, &c. 



It is to this stratum that the pentacrinitte seem peculiarly to belong. 

 These fossil remains occur with great frequency on the Dorsetshire coast. 

 When the vertebrae of this animal appear in any of the superior strata, 

 it is most probable, that they are alluvial, having been washed out of 

 the raised or basseting edges of this stratum, by that ocean which depo- 

 sited the stratum in which they are found. The confinement of the remains 

 of this genus of animals to so low a stratum, is very extraordinary, since 

 we have seen, that animals of this genus exist in the present ocean. 



Immediately above this stratum is a blue marl-stone, called the MAID- 

 WELL LIMESTONE, with the fossils of which I am unacquainted. Nor am 

 I able to speak with more information of a great number and thickness 

 of SANDS and CLAYS which lie over the Maidwell limestone. 



To these succeed the BATH FREE-STONE strata, which may be traced in 

 their range through the island. The upper part is a white or light grey 

 limestone; beneath which is the oolithe, or row-stone, and under this a 

 considerable thickness of very light coloured free-stone, then sand and clays, 

 and <a free-stone of various hues of yellow and red. 



The fossils of this strata are chiefly bivalve shells, of which generally 

 only the casts, or the impressions remain. The casts are chiefly of 

 arks, bucardita, (of Plott) a shell whose genus is not yet known, trigo- 

 nit, mytulita, and various other bivalves, the casts or impressions of 

 which only remaining, the genus of the shell cannot always be deter- 

 mined. Among the more perfectly preserved bivalves are several tere- 

 bratulitG, particularly the shell whose curious internal structure is figured 

 PL XVL Fig. 11 and 13, and which has been also mentioned and 



