326 APPENDIX. 



Pholadidea ? Tab. XXXI, fig. 23. 



This is the representation of a specimen obtained by Mr. John Middleton from the Crag "Diggings," 

 near Woodbridge, and obligingly put into my hands for publication by Mr. Woodward, who considers it a 

 genuine fossil of the Red Crag. It appears strongly to resemble the calcareous case of a species of boring 

 Mollusc, and the generic position he has chosen for it is probably the correct one, belonging to the 

 section Martesia, Gray. The interior is filled with mud or clay, and particles of sand, but the valves are 

 gone. The exterior presents concentric ridges or elevations (about a dozen) : these are in relief, and 

 correspond with the depressions or furrows often seen in the cavities formed by the Pholades. 



In my cabinet are some crypts of a similar form, excavated in a nodule of chalk found in the Red 

 Crag, evidently the production of a boring Mollusc. In my specimens the valves are gone, and the walls 

 in some of the cells are marked with concentric ridges. 



The following existing British species, not found in any of the Crag Formations, are enumerated as 

 belonging to the Upper Tertiaries of these kingdoms, in accordance with the authorities attached :* 



Patella pellucida. 



Irish Drift Beds. (Forbes.) 



Lucinopsis (Lucina) undata. 



Clyde Beds. (Smith.) 



Cardium aculeatum. 



Clyde Beds. (Smith.) 



CYPRINA PROPINQUA.f 



Clyde Beds. (Smith.) 



CYTHEREA L^VIGATA.f 



Clyde Beds. (Smith.) 



Venus verrucosa. 

 — striatula (gallina). 



Clyde Beds. (Smith.) 



* When the Palseontographical Society was first established the Crag Formations were the allotted 

 portions for my Monograph, while the more recent deposits of the British Isles were intended to form the 

 subject of a separate work by James Smith, Esq., of Jordan Hill ; and it was not until after the publication 

 of my first volume that any alteration was made in this arrangement. Mr. Smith found the fossils of these 

 Uppermost Tertiaries were, with so few exceptions, identical with existing species, that he thought they were 

 not of sufficient importance for a distinct work : it has therefore devolved upon me to mention those few 

 that have become extinct upon our own coasts, and this will in some degree explain the irregular and imperfect 

 manner in which I have introduced the species ; and as this has taken me rather beyond my original 

 intention, it has affected the correctness of my former title-page, and rendered it necessary to substitute a 

 new one. 



f These two species, noticed by Mr. Smith in his paper upon the ' Post-Tertiary Deposits of the Basin 

 of the Clyde,' ' Trans. Geol. Soc.,' 2d series, vol. vi, p. 155, he still thinks are decidedly distinct, and such 



