NUMERICAL ESTIMATE. 



347 



CONCLUSION. 



CHAPTER I. 



NUMERICAL ESTIMATE. 

 The number of living and fossil species of each genus of moUusca has 

 been stated in the preceding pages, so far as they could be ascertained. 

 Witli some modifications derived from recent data, these numbers give the 

 following totals, by which the relative numerical development of the orders 

 and families will be seen. 



Cephalopoda. 

 Argoiiautidte 

 Octojyodklae. . 

 Teuthidse . . 

 BelemnitidsB 



Sepiadee 



Spirulidse . . 



Recent. 

 Dibrandiiata. 



186 

 Tetrah) anchiata. 



Nautilidse 4 



Orthoceratidse ■ — 



Ammonitida? 



Gasteropoda. Prosob 



Strombidas* 



Muricidse 



Buccinidte 



Conidse 



Volutidae 



Cypraeid83 



Naticidie 



Pj'ramidellid£e 



Ceritliiadae 



Melauiadte 



Turritellidset 



Litoriuidae 



Paludinidse 



Calyptrasidse 



TurbinidfB 



Haliotidte 



Fissurellidae 



Neritidae 



Patellidfe 



Dentaliadae 



Cliitonidae 



4 

 •anchia 



83 

 870 

 1,048 

 856 

 686 

 225 

 245 

 216 

 192 

 424 

 196 

 315 

 132 

 160 

 855 



99 

 194 

 300 

 130 



50 

 230 



7,506 



Fossil 

 1 



31 



67 



1 



100 



174 



281 

 904 



1,359 



195 

 697 

 352 

 390 

 210 



97 

 340 

 322 

 610 



50 

 290 

 220 

 110 

 100 

 906 

 136 



72 

 100 

 100 



70 



24 



Eecent. Fossil 

 Puhiionifei^a. 



HelicidjB 3,900 280 



Limacidse 72 4 



Limnseidse 100 155 



(Marine) 86 28 



(Ditto, shell-less) ..16 



726 

 Tecti-hvanchiata. 



Tornatellida3 50 



Bullidffi 158 



Aplysiadse 79 



PleurobranchidaB 9 



Phyllidiadcs 10 



326 

 Nudibranchio ta. 



British 90 



Foreign 220 



310 

 Nttdcohranchiata. 



Shell-less 14 



Shell-bearing 30 



Pteropoda. 

 Hyaleidae . 

 Limacinidee 

 Cliusidce . . . 



152 



78 

 4 



100 

 100 

 32 



Including Aporrhais. 



t With Scalaria. 



