214 ORGANIC REMAINS. 



bodies, nearly in the shape of an echinus cidaris; but very differently 

 marked. Each of these bodies displays numerous strice, diverging- 

 from the centre to the disk, and passing down the sides ; and these 

 lines are crossed, especially on the disk, with several concentric 

 circles. These elevated lines, both longitudinal and transverse, are 

 in several places slightly tuberculated. We have not obtained a 

 complete specimen; but Fig. 14 of Plate VI will give some idea of 

 the appearance of these bodies. They are not entirely round, but 

 have four projections in the sides, presenting the appearance of a 

 square body, with its angles rounded off.* 



The ASTERiAS, or star-fish, is nearly allied to the echinus; but 

 Ave have found no petrified remains of that animal in the district. 

 We therefore proceed to the next and largest class of our petrifac- 

 tions, viz. 



TESTACEA, OR SHELLS. 



Were we to describe all the genera and species of shells, dis- 

 covered in a petrified state in this district, we should give the reader 

 an extensive system of conchology. The limits of our work will only 

 admit a sketch of the most interesting articles in this department. 



Shells are divided into three grand classes ; multivalves, con- 

 sisting of more valves or pieces than two; bivalves, or shells 

 having two valves ; and univalves, which consist of only one piece, 



* Since the description of the substance figured in Plate VI, No. 12, was printed, we 

 have examined some other specimens of a more decisive character, and have been led to 

 think, that it is a peculiar modification of petrified wood, similar to that described in Parkinson's 

 Org. Rem. V. I. p. 384. PI. VI. Fig. II, 16. We may add, that we have recently seen an 

 echinite of the helmet shape, from the Flamborough chalk, corresponding exactly with that in 

 Dr. Plot's Oxfordshire, Tab. II. Fig. 14, It is closely allied to that which we have given in 

 PI. VI. Fis-. 13. 



