EXPLANATION OF THE PLATES AND WOOD-CUTS. 



The species is very abundant. 



Loc. Marwood Quarry, where the shells of this and the following species of 

 Cucullcea are often replaced by quartz. 

 Fig. 24. Cucullaea Trapezium. Transverse, obtusely trapezoidal, oblong, irregularly 

 convex, smooth ; anterior side rounded ; posterior large, truncated, and longer 

 than the rest of the shell. Length about f ths of the width. 

 Loc. Marwood Quarry, Scarce. 

 Fig. 25. Cucullcea angusta. Squarish, rather wider than long, convex, smooth ; an- 

 terior side rounded, the posterior truncated, square ; beaks central. 



A cast has the impressions of the lateral teeth, which confirm the genus. 

 Loc. Marwood Quarry. 

 Figs. 26, 27. Cucullcea Hardingii. Transversely oval, with the posterior side trun- 

 cated, gibbose, smooth, nearly twice as wide as long ; beaks nearest the anterior 

 side. 



Loc. Marwood Quarry. 

 Fig. 27 is an end view of a smaller specimen. 



Fig. 28. Pullastra ? antiqua. Transversely elongato-ovate, slightly convex, concen- 

 trically striated, striae distant ; posterior extremity slightly and obliquely truncated. 

 Length about i the width. 

 Loc. Marwood Quarry. 

 Fig. 29. Leptcena prcclonga. Obovate, longer than wide, convex, with a depression 

 along the middle, coarsely and irregularly striated ; beak of the larger valve in- 

 flated and overhanging the smaller one, which is concave ; margin much deflected ; 

 hinge-line shorter than the width of the shell ; a few slight concentric waves pro- 

 ceed from it. 



Loc. Croyde Bay, in a harder stone than the Marwood Bay fossils. 

 Fig. 30. Hellerophon globatus. (Silur. Syst. PI. IIL fig. 15.) We can perceive no 

 diflPerence between this fossil and some specimens from the lower beds of the old 

 red sandstone. 

 Loc. Marwood. 

 Fig. 31. Crinoidal casts abundant at Croyde Bay. 



Plate LIV. 



Fig. 1. Avicula [Monotis, Bronn) subradiata. Obliquely ovate, with one rectangular 

 ear smooth, with a few concentric lines, and radiated principally along the middle; 

 one valve flat, the other convex ; anterior extremity rounded, small. Width con- 

 siderably more than the length. 

 Loc. Petherwin. Frequent. 

 Fig. 2. Avicula Pectinoides. Suborbicular,flattish, radiated ; ears very large, square; 

 the posterior slightly sinuated. 



This specimen, which is very imperfect and worn, resembles A. Isleptuni (Goldf. 

 Pet. CCXVL fig. 4), but wants the numerous concentric striae which ornament that 



