EOCENE PERIOD. 551 



those now existing. The Tabulata are represented by no 

 more than one genus, and the Eocene forms belong mainly to 

 the Zoantharia, Aporosa, and Perforata. Besides Zoantharia, 

 the family of the Pennatulidce (Sea-pens, &c.) is represented 

 by the genus Graphularia, and the family of the Gorgonidce 

 (sea-shrubs), by the genera Mopsea and Websteria. 



As regards the Mollusca, Brachiopods and Polyzoa are not 

 abundant, and the former are represented in Eocene times 

 chiefly by the existing genera Terebratula and Rhynchonella, 

 Lamellibranchs and Gasteropods, the latter especially, are 

 exceedingly abundant, and almost all existing genera are now 

 represented ; though less than five per cent are identical with 

 existing species. The Gasteropods are chiefly siphonostoma- 

 tous, and belong to such familiar genera as Valuta, Mitra, 

 Conus, Pleurotoma, Fusus, Cyprcza, Oliva, Ancillaria, Rostel- 

 laria, &c. The fresh-water and brackish-water beds of the 

 formation have also yielded numerous species of Cerithium, 

 along with Limncea, Planorbis, Melania, &c. The Ammonites, 

 Turrilites, B acuities, Belemnites, &c., of the Cretaceous period 

 have now disappeared, and the Cephalopoda are represented 

 mainly by the genus Nautilus, though Dibranchiates (such as 

 Belosepid) are not unknown. 



The most important fossils of the Eocene Rocks belong to 

 the sub-kingdom of the Vertebrata. Fishes are numerous, 

 sometimes (as in the limestone of Monte Bolca) extraordinarily 

 so. They belong in the vast majority of instances to the 

 Teleostei, the remains of Ganoid fishes being comparatively 

 very rare. True Sharks are represented by numerous teeth, 

 referable to the genera Carcharodon, Otodus, Lamna, Galeo- 

 cerdo, &c. ; and Rays are represented by their pavement-like 

 dental plates (Myliobatis}. 



The Reptiles of the Eocene period all belong to the existing 

 orders of the Chelonians, Ophidians, Lacertilians, and Croco- 

 dilians. The Chelonians are very abundant, and belong for 

 the most part to existing genera. The Ophidians make their 

 first appearance in the Eocene (Palceophis). The Crocodilians, 

 lastly, are very abundant, speaking comparatively ; and Eng- 

 land possessed in Eocene times representatives of the three 

 existing genera of this order viz., Crocodilus, Alligator, and 

 Gavialis. 



As regards the Birds, it is sufficient to say that all the exist- 

 ing orders of Aves appear to have been represented in Eocene 

 times, often by forms which differ little from existing types. 



As regards the Mammals, the Eocene deposits have yielded 

 remains of Marsupialia, Sirenia, Cetacea, Ungulata, Carnivora, 



