50 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



to some few cases, which might be exceptional, but every individual 

 has dimensions exceeding the largest known recent examples. 



The perforations made by this mollusk are filled with fine sand, such 

 as forms occasionally the lowest portion of the " mud-deposit ;" and 

 it is in these cavities, and between the valves of the Pholades, that 

 some of the characteristic shells to be noticed have occurred, such as 

 the Fecten polymorphus. The largest that I have seen of these Pho- 

 lades measured six inches in length ; and it is somewhat strange that 

 so remarkable a form, which has been known to shell-collectors for 

 some time, should not have succeeded in drawing attention to the 

 inquiry as to what species might be associated with it in the same 

 beds.* 



The Pholas crispata is not only a littoral species, but is one 

 which, from its very restricted range, serves well to determine the 

 level of the tidal waters at the commencement of the Selsea deposits. 



Fossils of the Mud-deposit^ and its relative age. — The only Mam- 

 malian remains which have been found in this old estuarine deposit 

 of Selsea are those of the Elephas primigenius ; these are tolerably 

 abundant : and there is this point of geological interest attaching to 

 these specimens, that they do not here occur as single and detached 

 teeth, or portions of tusks, as happens in the overlying gravel-beds ; 

 but so many parts of the animal have been found together, as to leave 

 no doubt but that entire skeletons lie embedded in this deposit. Such 

 was certainly the case in one instance which came to my knowledge, 

 where the head, with the teeth and tusks, and numerous bones lay 

 together in close juxtaposition. 



Gasteropods. 



Fusus turricula, Mont. [Mangelia^ [Clavatv.la, Lam.]. 



Living, and common on all British Coasts, but essentially a 



Boreal Atlantic species. 

 Fossil, in the Red Crag, common ; also in the Faluns [Pleuro- 



toma clavula, Duj.], where it is scarce. Bridlington. 

 Buccinum undatum, Lam. 



Living in the Northern Atlantic, but does not extend to the 



Coast of Spain. 

 Fossil ; in the Coralline Crag scarce, in Red Crag common ; 



and extended into the Mediterranean at the time of the 



Sicilian beds. — Philippi ; vol. i. p. 226. 

 Nassa reticulata, IjiiLm.-= Buccinum. 



Living ; has a wide range ; common on all British Coasts ; 



Mediterranean. A salt-lagoon shell. — Phil. 

 Fossil ; Mr. S. Wood states that he has not seen an undoubted 



specimen of this species from any of the three divisons of 



the Crag formation. Monog. Crag Moll. p. 33. It is not 



quoted by Philippi as occurring in the Sicilian beds. 

 CyprcBa europcea. Lam. "^ 



Living ; common on all British Coasts. 



* I have been informed that these Pholades were considered by most collectors 

 as recent and not as fossil shells. 



