20 INVERTEBRATE ANIMALS. 



by the late S. P. Woodwabd, and the " Manuel de Conchyliologie,'" 

 by M. Chend, have been followed in arranging the fossil illustra- 

 tions. Of the 1390 Generic and Sub-Generic forms recognised in 

 the "Genera of Recent Mollusca,^^ the collectio7i at present contains 

 illustrations of about 1121. The "History of Britis i Mollusca and 

 their Shells" by Edward Forbes and S. Hanlet, has been used in 

 naming and arranging the British representatives in the 78 groups 

 assigned to the Mollusca Proper. 



Class LAM ELLI BRANCH I ATA. lamina, a 

 plate ; (Bpayxta, the gills of fish. = CONCHIFEEA 

 (Lamarck). Bivalve Mollusca. 

 Section ASIPHONIDA. a, without ; a-i^m, a tube. 



The absence of a respiratory siplioti indicates, generally, that the 

 species do not live immersed in sand or mud. 



Group 55.— Family OSTR^ID^ and allies. Oyster. 

 Estimated number of species : recent, 182 ; British, 5 ; 

 fossil, 200. Carboniferous, &c. 



H Examples of Ostrea, Anomia, Plicatula, Spon- 

 dylus, Placunanomia. 



Upper Compartment. 



Placenta orbicularis, used for windows in some 

 parts of China ; Group of Pedum in coral of 

 the genus Porites. 



Group 56.— Family PECTENID^ and allies, pecten, a 

 comb. Estimated number of species : recent, 220 ; 

 British, 13 ; fossil, 600. Carboniferous, &c. 



IT Examples of Pecten, Lima, Radida, Hinnites. 

 P. Proteus, exhibiting contrasts of colour between 

 specimens of the same species. Lima excavata, 

 North Sea. R. M'Andrew. 



Group 57. — Family ARCID^E and allies. a7'ca, a chest. 

 Estimated number of species : recent, 341 ; British, 11 ; 



