PLATE VIII. 



The following Letters refer to the same parts and impressions in every figure. 



A, adductor muscles {add. longus, Owen) ; R, cardinal muscles (add. brevis and cardinalis, Owen) ; 

 p, pedicle muscles {retractor sup. and inf., Owen); J, cardinal process; L, loop; t, teeth; 

 B, sockets ; D, deltidium ; v, vascular impressions ; o, ovarian spaces ; s, septum, &c. 



Fig. 



136. Orthis rustica, Sow. 



137. „ ,, Interior of dorsal valve. 



138. „ „ Interior of ventral valve. 



139. „ „ The double area and fissures. 



140. „ elegantula. 



141 — 144 „ biloba, Linn., sp. = genus Diaslosia, King. 



145. „ „ Interior of dorsal valve. 



146. „ biforata, Sch., sp. = genus Platystrophia, King. 



147. „ „ InterioT oi ventral OT dental valve. 



148. „ „ Interior of dorsal or socket valve. 



149. Orthtsina adscendens, Pander, sp. = genus Pronites and Hemipronites, Pander. 



150. „ anomala, Schl., sp. 



151. „ „ Interior of dorsal valve, from a specimen in the collection of M. de 



Verneuil, 



152. „ hemipronites. Viewed from the beaks, to illustrate the double area and closed fissures. 



153. „ jdana. Interior of ventral valve, from a specimen in the collection of M. de Verneuil. 



154. „ „ Interior of dorsal valve. 



155. „ 1 senilis, viewed from the beaks. 



156. „ 1 pelargonatus = genus Streptorhynchus, King. 



157. Strophomena planumbona, Hall. {Dorsal valve convex.) 



158. „ „ Interior of ventral valve. 



159. „ „ Interior of dorsal valve. 



160. „ a^^erMote (Conrad), \nimov oi dorsal valve. 



161. „ „ Fragment of the beak, to show the position of the foramen. 



162. „ expansa. Sow., sp. Drawn partly from the original specimen, figured by Sir 



R. Murchison, in the 'Silurian System,' pi. xx, fig. 14 ; and 

 from another example in the Mus. of Prac. Geol. 

 164. „ pecten, Linn., sp. 



„ narangoana, Vern., sp. No fissure or deltidium interrupts the area. 



„ latissima, Bouchard. Ibid. 



168. „ depressa or rhomboidalis. No foramen seen in this specimen. 



„ „ Young example of the same, from Dudley, in which the perforation or 



temporary foramen is clearly seen. 

 „ „ Interior of dorsal valve. 



„ ,, Interior of ventral valve. 



„ „ Section of the valves. 



„ „ Interior of ventral valve, from a specimen from Gothland, in the collec- 



tion of Professor King, showing curious sub-spiral labial impressions ; 

 a similar example has been figured by Professor Quenstedt. (Hand- 

 buch der Petref. tab. xxxix, fig. 20.) 



163, 

 165. 

 166. 

 167, 

 169. 



170. 

 171. 

 172. 

 173. 



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