EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Fig. 7. Spirifera calcarata. Semicircular, with extended cuspidate smooth sides, sul- 

 cated, very convex ; front scarcely at all elevated ; ribs numerous, rounded, wiili 

 about nine on the front bounded by two deep furrows ; area probably very 

 narrow. Width more than twice the length. 



This approaches closely to S. attenuata, M. C, but is distinguished by the 

 sudden contraction of the sides, and the very slight elevation of the front ; still we 

 have some doubts of its being distinct from the many varieties of that species. The 

 characters are taken from a single internal cast. 

 Loc. Barnstaple. 

 Fig. 8. Spirifera disjuncta. This, which is a cast of the inside of the upper valve, 

 appears to belong to the species thus named, and is a good illustration of the in- 

 ternal structure of the genus, exhibiting the beak, the muscular impressions, the 

 central striated foramen, and also the hinge area with its striated structure. 

 For a further description, see PI. LIV. figs. 12 and 13. 

 Loc. Barnstaple. 

 Fig. 9. Spirifera inornata. Fusiform, compressed, smooth, obscurely radiated on the 

 sides ; the front even ; beaks obscure. Length scarcely more than \ of the width. 

 This is so much crushed and distorted, that it is impossible to give a full de- 

 scription ; but it appears to be distinct from every other species, approaching 

 nearest in form to the Orthis {Spirifera) alata of the Silurian System, PI. 22, f. 7. 

 Loc. Ilfracombe. 

 Fig. 10. Orthis plicata. Transversely elongated, depressed, plaited; plaits numer- 

 ous, sharp ; width twice the length. 



This resembles O. radians {Si\u.y. Syst. PI. 22, f. 11), but has much more nu- 

 merous plaits. 

 Loc. Barnstaple. 

 Fig. 11. Orthis interlineata, A distorted cast, which may easily be mistaken for O. 

 canalis (Silur. Syst. PI. 22, fig. 8) or O. testudinaria (figs. 9 and 10). 



Fuller details are given in the description of the Petherwin fossils, PI. LIV., 

 Fig. 14., where better specimens are figured. 

 Loc. Leary, N. Devon, &c. 

 Figs. 12 — 15. Calymene. Figs. 12, 13, 15, Barnstaple. 14, Saunton. 

 Figs. 17 — 21. Crinoidal remains. 17, Barnstaple. 18, 19, 21, Redruthen Steps, in St. 



Eval. 20, Lower St. Columb, Perth. 

 Fig. 22. Avicula Damnoniensis. Obliquely ovate, with a square projecting ear, very 

 convex, short, striated ; anterior side small, obtuse ; hinge-line rather shorter than 

 the width of the shell ; beaks large, convex near the anterior extremity ; poste- 

 rior slope and ear destitute of the fine longitudinal striae which ornament the rest 

 of the shell. 



Abundant in the soft ferruginous sandstone in which the fossils of Marwood 

 Quarry are all imbedded. 

 Fig. 23. CucullcBa unilateralis. Obliquely ovate, gibbose, smooth ; posterior side ob- 

 lique, flattened ; beaks nearest to the anterior side. 



The cast^figured shows the impression of the internal lamina peculiar to the genus. 



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