38 LITERATURE OF THE MOLLUSC A 



only in the Devonian, and the Dibranchs (Belemnites) at the 

 beginning of the Secondary. But at the present day all the species 

 of Tetrabranchs, some 7500 in number, are only represented by 

 a few species of the single genus Nautilus ; and as for the group of 

 Belemnites; it has entirely disappeared since the end of the 

 Cretaceous, its sole surviving and more or less distant represent- 

 ative at the present day being the genus Spirula. 



Among the Gastropods the Aspidobranchs (Rhipidoglossa) are 

 the first to appear; several families, such as the Capulidae and 

 Pyramid ellidae, date back to the Upper Silurian. On the other 

 hand, there are but few Ctenobranchs in the Palaeozoic ; most of 

 the families of this order make their appearance in the Secondary, 

 and the same may be said of the Opisthobranchs, with the 

 exception of the Actaeonidae, which are found, as also are the 

 Pulmonata, in the Carboniferous. Of Lamellibranchs various 

 Protobranchs and Filibranchs are found in the Silurian, but the 

 other groups, as a rule, do not appear till the Secondary. The 

 Palaeoconcha of the Primary, and the Rudistae, Diceratidae, Mono- 

 pleuridae, and Caprinidae of the Secondary, have died out without 

 leaving descendants. 



LITERATURE OF THE MOLLUSCA GENERALLY. 

 I. Conchological. 



1. Cooke. Molluscs. The Cambridge Natural History, vol. iii. 1895. 



2. FiscJier. Manuel de Coiichyliologie, 1887. 



3. Jeffreys. British Conchology, 1862-1869. 



4. Simroth. Mollusca. Bronn's Klassen und Ordnungen des Thierreichs, 



Bd. iii. 1895 till now. 



5. Taylor. Monograph of the Land and Freshwater Mollusca of the British 



Isles, 1900 till now. 



6. Tryon. Manual of Conchology, 1878 till now. 



7. Woodward. A Manual of the Mollusca, 1880. 



II. Morphological. 



7 bis. Cuenot. L'excre"tion chez les Mollusques. Arch. d. Biol. t. xvi. 1899. 



8. Qeddes. On the Mechanism of the Odontophore in certain Mollusca. Trans. 



Zool. Soc. London, vol. x. 1879. 



9. Huxley. On the Morphology of the Cephalous Mollusca. Phil. Trans. 1853. 



10. von Jhering. Vergleicheude Anatomie des Nervensystemes und Phylogenie 



der Mollusken, Leipzig, 1877. 



11. Die Gehbrwerkzeuge der Mollusken, Erlangen, 1876. 



12. Zur Morphologic der Niere der sog. " Mollusten. " Zeitschr. f. wiss. 



Zool. Bd. xxix. 1877. 



13. Lankcster. Mollusca. Encyclopaedia Britannica, 9th edit. vol. xvi. 1883. 



14. Contributions to the Developmental History of the Mollusca. Phil. 



Trans. 1875. 



15. Note on the Coelom and Vascular System of Mollusca and Arthropoda. 



Quart. Journ. Micr. Sci. vol. xxxiv. 1893. 



