430 IDENTITY OF FOSSIL WITH LIVING 3I0LLUSCA. chap. xxii. 



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 majorit}' of living species. For what we want is 

 time, first for the gradual formation, and then for the ex- 

 tinction, 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 Falu- 

 nian or Upper Miocene strata of Europe belonged to living 

 species. Although the soundness of that conclusion Avas 

 afterwards called in question by two or three eminent concho- 

 logists (and by the late M. Alcide d'Orbigny among others), 

 it has since been confirmed by the majority of living natural- 

 ists, 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 w^ere 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 disappearance 

 by extinction of intermediate varieties and species. 



