owen. 583 



Fan). 8. CamacAs, Lamarck. Genera — Etheria, 

 Chama, Diceras, Caprina, Isocardia, Tridacna, Hip- 

 popus. 



Fam. 9. Conchaces, Blainville. Genera — Iridina, Car- 

 dium, Hemicardium, Capsa, Donax, Gratelupia, 

 Tellina, Lucina, Corbis, Ampliidesma, Cyprina, 

 Mactra, Erycina, Cyclas, Cyrena, Galathea, Cras- 

 satella, Astarte, Venus, Venerupis, Petricola, Coral- 

 liophaga, Clotho, Ungulina. 



Fam. 10. Pylorides, Blainville. Genera — Corbula, 

 Pandora, Thracia, Periploma, Anatina, Mya, Lutra- 

 ria, Psammocola, Soletellina, Sanguinolaria, Sole- 

 curtus, Solen, Solemya, Glycimeris, Panopaea, 

 Saxicava, Byssomia, Rhomboides, Hiatella. 



Fam. 11. Tubicoles, Lamarck. Genera — Aspergil- 

 lum, Clavagella, Gastrochsena, Pholas, Jouannetia, 

 Teredo, Fistulana, Septaria, Teredina. 



2 Section Acephales non Testaces, Cuvier. 

 Order IV. Heterobranches, Blainville. 



Fam. 1. Ascidiens, Lamarck. Genera, — Ascidia, 

 Bipapillaria, Fodia, Pyura, Distoma, Botryllus, 

 Synoicum. 



Fam. 2. Salpiens, Blainville. Genera — Salpa, Ti- 

 moriensis, Monophorus, Phylliroe, Pyrosoma. 



A sort of commentary on the leading sections of this table 

 will lead me as far as I intend to guide you in this field. 



1. Cephalopoda. 

 In 1825, M. de Haan, and in 1826, M. D'Orbigny pub- 

 lished the results of their study of this class, more especially 

 of its fossil constituents : and they made a large increase to 

 our knowledge of their structure. The researches of D'Or- 

 bigny were more general and comprehensive than those of 

 the Dutch naturalist, and M. Rang has availed himself of 

 them only in his arrangement, which is to be considered as 

 a literal reproduction of his countryman's method, — the 

 families and genera standing in the same relation to each 

 other, and under the same designations. Shortly afterwards 

 three discoveries contributed to alter the systematic view of 

 the class. The first was Professor Owen's Anatomy of the 

 Nautilus pompilius, published in 1832,* whereby our almost 

 conjectural notions of the tenants of the polythalamous shells 

 were swept away, and certain knowledge substituted in their 

 place. The second was the ascertainment of the simple and 



* Memoir on the Pearly Nautilus, &c. By Richard Owen. Loud. 1832. 4to. 



