TABLE OF CHARACTERISTIC GENERA. 



239 



last are the most precious for geologists, because thev become 

 characteristic." 



TABLE OF CHARACTERISTIC GENERA. 



Systems. 



G-ENERA AITD SlTB-GENERA. 



1. Cambrian, or 

 Lower Silurian. 



2. Silurian. 



3. Devonian. 



4. Carboniferous. 



5. Permian 



6. Trias 



7. L. Jurassic 



8. U. Jurassic 



9. L. Cretaceous.. 

 10. U. Cretaceous.. 



p Cameroeeras. Endoceras, Gonioceras, Pterotheca. 



} Maclurea, Raphistoma, Holopea, Platyceras. 



] Orthisina, Platystropliia, Porambonites, Pseudo-crauia. 



[ Ambonj'cliia, Modiolopsis, Lyrodesma. 



Actinoceras, Plaragmoceras, Troclioceras, Ascoceras. 



Theca, Holopella, Murcliisonia, Atrypa, Retzia. 



Cardiola, Clidophorus, Goniophorus, Grammysia. 



Bactrites, Gyroceras, Clymenia, Apioceras, Serpularia. 



Spirifera, Uncites, Merista, Uavidsonia, Calceola 



Stringoceplialus, Megalodon, Urthonota, Pterinea. 



Nautiloceras, Discites, Goniatites, Porcellia. 



Naticopsis, Platycliisma, Metoptoma, Pi'oductu.s. 



Aviculo-pecten, Anthi-acosia, Conocardium, Sedgwickia. 

 f Camaroplioria, Aulosteges, Strophalosia. 

 \ Myalina, Bakewellia, Axinus, Edmondia. 



11. Eocene... 



12. Miocene., 



13. Pliocene 



Ceratites, Naticella, Platystoma, Koninckia, Cyrtia. 

 Monotis, Myophoria, Pleurophorus, Opis. 

 Belemniies, Beloteutliis, Geoteuthis, Ammonites. 

 Alaria, Trochotoma, Rimula, Pileolus, Cylindrites. 

 Waldlieimia, Theddium, Spiriferina, Ceromya. 

 Grypliaea, Hippopodium, Cardinia, Myoconcha. 

 Coccoteutbis, Leptoteuthis, Nautilus. 

 Spinigera, Purpurina, Nerineea, Neritoma. 

 Pteroperna, Trichites, Hypotrema, Diceras. 

 Trigonia, Pachyi'isma, Sowerbia, Tancredia. 

 Criocei'as, Toxoceras, Hamulina, Baculina. 

 Requienia, Caprinella, Spheera, Thetis. 

 Belemnitella, Conoteuthis, Turrilites, Ptychoceras. 

 Hamites, Scaphites, Pterodonta, Cinulia, Tylostoma. 

 Acteonella, Globiconcba, Trigonosemus, Magas, Lyra. 

 Neithea, Inoceramus, Hippurites, Caprina, Caprotina. 



Beloptera, Lychnus, Megaspira, Olandina, Typhis. 

 VolutUithes, Clavella, Pseudoliva, Seraphs, Rimella. 

 Conorbis, Strep^idura, Globulus, Phorus, Velates. 

 Chilostoma, Volvaria, Lithocardium, Teredina. 

 Spirulirostra, Aturia, Vaginella, Ferussina. 

 Halia, Proto, Desliayesia, Niso, Cassidaria, Carolia. 

 Grateioupia, Artemis, Tapes, Jouannetia. 

 Argonauta, Strombus, Furpura, Trophon. 

 Yoldia, Tridacna, Circe, Verticordia . 



In the above table will be found the list of 13 geological 

 systems, each having a certain number of special genera. Some 

 of the genera cited, for example, Belemnites, have a greater 

 extension, but are mentioned by reason of their abundance in a 

 particular system. Names in italics are those of living genera. 



The following table contains some of the larger genera arranged 

 in the order of their appearance. 



