EXPLANATION OF PLATES. 299 



FIG. 



175. Dianchora striata, (from Sow. Min. Con.) 



176. Plagiostoma spinosum, (from Sow. Min. Con.) 



177. Spondylus Americanus, hinge. (See Frontispiece.) 



178. Plicatula gibbosa. Harpax, Parkinson. 



179. Pedum Spondyloideum, (from Sow. Gen.) 



Fam. Ostracea. 



180. Ostrea edulis. 



181. Folium. Dendostrea, Sw. 



182. Grypheea incurva. 



183. Exogyra conica, (from Sow. Min. Con.) 



184. Placuna placenta. Gen. Placenta, Schum. 



185. Vulsella lingulata. 



186. Anomia Ephippium. 



187. Hinge of the same, with bony process. 



188. Hinge, showing the fissure. 



189. Placunanomia Cumingii. 



190. Hinge of the same, showing the fissure. 



191. Hinge of the unattached valve. 



192. Mulleria. (from Sow. Gen.) 



Fam. Rudistis. 



193. Sphserulites foliacea. (Radiolites is more conical.) 



194. Calceola Sandalina. 



196. Birostrites insequiloba, internal cast of Sphaerulites. 



197. a. Crania personata, dorsal valve ; b. C. antiquata, interior. 



(This would be more properly placed in Brachiopoda.) 



198. Hippurites Cornucopia, (from Blainville.) 



199. Hipponyx Cornucopia, attached valve. 



200. Upper valve of the same. 



Fam. Brachipoda. 



201. Orbicula lsevis. 



202. Terebratula Psittacea; a. anterior margin, 



203. Atrypa reticularis. Trigonotreta, Konig. 



204. Cyrtia exporrecta, 



