ANNIVERSARY ADDRESS OF THE PRESIDENT. 



xlvii 





Brach. 



Monom. 



Dimy. 



Oast. a. 



Gast.A. 



Cephal. 



Fishes. 





2 

 10 



9 



15 



15 



*18 



v. 



Infu 



7 

 13 

 *17 

 9 

 3 

 5 



45 

 44 

 46 

 35 

 16 

 17 



51 

 18 

 37 

 20 

 9 

 18 



27 



10 



9 



1 





 



4 



*12 



5 



7 

 5 

 5 



60 

 45 

 49 

 60 

 35 

 4 



Cretaceous 



Oolitic 



Carboniferous .... 







r * 



sorial Feeders. 



Herbivorous and 

 Carnivorous. 



Carnivorous. 



Some years since (1842-44), while engaged in discussing the large 

 collections of Lower Palaeozoic Fossils for my Memoir on Malvern, 

 I found reason to remark on tho very limited molluscous fauna of 

 the whole Silurian scries in the south-west of Wales, — and in regard 

 to the Conchifera, to remark that in that whole district all the forms 

 appeared reducible to three great families — Aviculaceao, Mytilaccoo, 

 and Arcacese. If we trace in a diagram the geological distribution 

 of these families, it appears that hardly any bivalves, except such as 

 belong to Aviculaceee and Arcaeeae, occur ; Mytilacea? (with what I 

 regarded as' allied forms, viz. Goniophora and Orthonota) abound in 

 the Upper Silurians. Once introduced, these groups never cease to be 

 traceable through all the range of the strata ; and some of the genera 

 are continuous even from the Lower Palaeozoic to tho latest Tertiaries 

 and to the existing ocean. It seems, however, that two at least of 

 these families may be regarded as having passed the maximum. If 

 we compare with these the large groups of Liniidae, Ostrooidae and 

 Trigonidae, none of which really appear in the Lower Palaeozoic 

 strata, we find them to have their origin (with only a doubtful 

 exception in Limcm) in tho Mesozoic series, to have in that their 

 capital, and to be now reduced to a few representatives in nature. 

 Pectinidae, on the other hand, exhibit an intermediate character — 

 rising, in the groups above the Silurian, to a maximum in the 

 Mesozoic series, and being still an abundant group in the sea. 



In tracing the history of some of these ancient families of ftfolluBCa 

 through the long eouxse of geological time, hardly anything is more 

 striking than the continuity of the character of each family, and the 

 small additions which are made to it by ramtficationfl of any kind. 

 Side by side with them grow np in later ages many ether families, as 

 the Cardiaoees, Veneridae, ICyadss. These do not appear to replace 

 the older types ox to be derived from them. bn1 to take parallel ami. 



it may be said. ind<]i-'nd< n! 0001860, BO B8 to SQggesI to us. gg to OUT 



lamented Forbes, the coin-cptioii of I'jiuchs rich in additional generic 

 ideas,- — a poetical mode of expression not really clearer or more prei ise 

 than that of W. Smith, who regarded the life of each natural group 

 of strata as a separate creation — in which he if completely followed 

 by D'Orbigny and a hosi of modern writers. 



If in the same manner we trace the families of the purely carni- 

 vorous group of Cephalopoda, the result will be very different. Or- 



thot cratid;e commence in the Lower 1'aln-ozoic, ami end in the 



