430 IDENTITY OF FOSSIL WITH LIVING MOLLUSCA. CHAP. xxrr. 



the recent or fossil fauna, are eagerly sought for, and often 

 more prized than the mere normal or typical forms. 



It is clear, that the more ancient the existing mollusca, or 

 the farther back into the past we can trace the remains of 

 shells still living, the more easy it becomes to reconcile with 

 the doctrine of transmutation the distinctness in character of 

 the majority of living species. For, what we want is time, 

 first, for the gradual formation, and then for the extinction 

 of races and allied species, occasioning gaps between the 

 survivors. 



In the year 1830, I announced, on the authority of 

 M. Deshayes, that about one-fifth of the mollusca of the 

 Falunian or Upper Miocene strata of Europe, belonged to 

 living species. Although the soundness of that conclusion 

 was afterwards called in question by two or three eminent 

 conchologists (and by the late M. Alcide d'Orbigny among 

 others), it has since been confirmed by the majority of living- 

 naturalists, and is well borne out by the copious evidence 

 on the subject laid before the public in the magnificent work 

 edited by M. Homes, and published under the auspices of 

 the Austrian Government, ' On the Fossil Shells of the 

 Vienna Basin.' 



The collection of tertiary shells from which those descrip 

 tions and beautiful figures were taken is almost unexampled 

 for the fine state of preservation of the specimens, and the 

 care with which all the varieties have been compared. It is 

 now admitted that about one third of these Miocene forms, 

 univalves and bivalves included, agree specifically with living 

 mollusca, so that much more than the enormous interval 

 which divides the Miocene from the Eecent period must be 

 taken into our account when we speculate on the origin by 

 transmutation of the shells now living, and the disappear 

 ance by extinction of intermediate varieties and species. 



