546 HISTORY OF SYSTEMS. 



Section I. Shell symmetrical. The genera are — 

 Lingula. Terebratiila. 



Thecidea. Strophonema. 



Plagiostoma. Dianchora. 



Podopsis. 



Section II. Shell non-symmetrical, irregular, attached. 

 Orbicula. Crania. 



Order II. Rudista. The genera are — 



Spherulites. Hippurites. 



Radiolites. Birostrites. 



Calceola. 



Order III. Lamellibranchiata = Acephales testaces, 

 Cuv. 

 Family 1. Ostracea. The Genera are Anemia, Pla- 

 cnna, Harjaax, Ostrea, Grypha?a. 



,, 2. Subostracea. Gen. : Spondylus, Plica- 

 tula, Hinnites, Pecten, Pedum, Lima. 



„ 3. Margaritacea. Gen. : Vulsella, Malleus, 

 Perna, Crenatula, Inoceramus, Catillus, Pulvi- 

 nites, Gervillia, Avicula. 



,, 4. Mytilacea. Gen. : Mytilus, Pinna. 



,, 5. Polyodonta. Gen.: Area, Pectunculus, 

 Nucula. 



,, 6. SuBMYTiLACEA. * Species with an epi- 

 dermis, nacred, fluviatile. Anodonta, Unio. — 

 ** Species without a distinct epidermis, not 

 nacred, and more or less pectinate : marine. — 

 Cardita. 



J, 7. Camacea. * Shell irregular. Cliama, Di- 

 ceras, Etheria. ** Shell regular. Tridacna, 

 Isocardium, Trigonia. 



„ 8. Conch acea. Section 1. Regular with 

 distant lateral teeth. Cardium, Donax, Tellina, 

 Lucina, Cyclas, Cyprina Mactra, Erycina. Sec- 

 tion 2. Regular without separate lateral teeth. 

 Crassatella, Venus. Section 8. Irregular. Vene- 

 rupis, Coralliophaga, Clotho, Corhula, Sphsena, 

 Ungulina. 



,, 9. Pyloridea. Section 1. Ligament inter- 

 nal. Pandora, Anatina, Thracia, Mya, Lut- 

 ricola. — Section 2. Ligament external and swol- 

 len. Psammocola, Soletellina, Sanguinolaria, 

 Solecurtus, Solen, Solemya, Panopaea, Glyci- 

 mera, Saxicava, Byssomya, Rhomboides, Hia- 

 tella, Gastrochaena, Clavagella, Aspergillum. 



