EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Plates L. and LL 

 Map and Sections of Devonshire and Cornwall. 



Plates LIL to LVII. 



Organic remains engraved and described by Mr. James de Carle Sowerby. May, 1840. 



Plate LII. 



(Fossils from Barnstaple.) 

 Fig. 1. Postdonia (Bronn.) lateralis. Compressed, transversely elongate-ovate, con- 

 centrically ridged ; umbones very near the anterior extremity ; ridges angular. 

 Width about 2^ times the length, which is If inch. 

 Loc. Venn Lime Quarry, near Barnstaple. 

 Fe^. 2 and 3. Posidonia Becheri. (Goldf. Petref. 119. t. cxiii. f. G a. Bronn. Leonh. 

 Zeitsch. f. Mineralog. 1828, April, t. ii. f. 1—4.) 



Compressed, ovate, concentrically ridged, and finely striated ; posterior slope 

 straight ; ridges numerous ; umbones nearest the anterior side. Width in pro- 

 portion to the length as 7 to 4. Its length is about If inch. 

 Fig. 3 is from a specimen with fewer ribs. 



Loc. Venn Quarry. Swimbridge Quarry. 

 Fig. 4. Posidonia Becheri, var. (Goldf. loc. cit. f. G h. c.) Slightly convex, obovate, with 

 the posterior extremity nearly square ; concentrically ridged and finely striated ; 

 umbones close to the anterior extremity. Width rather more than the length, 

 which is nearly \\ inch. 

 Loc. Venn Quarry^ 



We have seen specimens of this shell from Herborn, near Dillenberg, and Schelke 

 in Westphalia, where other species of the genus are also found. 



We can hardly believe this and the preceding to be the same species ; but we 

 yield to Goldfuss, who has had more specimens to examine than have come under 

 our observation. 

 Fig. 5. Posidonia tuberculata. Compressed, obovate, approaching orbicular, concen- 

 trically ridged, and marked down the middle with three or four longitudinal ribs, 

 which form more or less distinct tubercles as they cross the ridges. Length not 

 2\ inches, and width full 2| inches. 



Loc. The specimen figured is from Buddie, near Bamborough. 

 We have examined one from Devonshire, which has the tubercles much more 

 strongly marked. 

 Fig. G and 7. Orthoceras cylindraceum. A much elongated, smooth species, with ra- 

 ther distant septa. The specimens are too imperfect to be positively identified ; 

 the name must therefore be considered only as temporary. 

 Loc. Venn and Swimbridge Quarries. 

 Fig. 8 and 9. Goniatites carbonarius. Although we have seen many specimens of 



