2 bulletin: museum of comparative zoology. 



extent of variation and specialization that has been going on in certain 

 groups during this interval. But the most striking fact which arrests 

 our attention is not that variation should have advanced at sucli a slow 

 rate since Eocene times as it apparently did, but that this process 

 should have been quickened by such a sudden and enormous accelera- 

 tion as took place at the dawn of the Tertiary system. Cretaceous 

 forms pass away, leaving only here and there a few moribund survivors 

 {e. fj. Pycnodua, Palaeohalistum, etc.) in the Eocene, their place being 

 taken by a host of modern types which appear for the most part ab- 

 solutely unheralded. Xot only does the Eocene fish fauna bear an 

 overwhelmingly moderu aspect, but many of its types are as highly 

 specialized as they are to-day ; and forms which at the present day are 

 widely aberrant have representatives at least as far back as the Middle 

 Eocene. It is evident that an "expression point" (to us Cope's apt 

 term) was reached in the evolution of ichthyic life exactly correspond- 

 ing to, and contemporaneous with that which is so well recognized in 

 mammalian life, although the cause of the phenomena is in each case 

 unknown. 



The literature of Bolca fishes is extensive, and material from the 

 typical locality has become distributed throughout the principal museums 

 of the world. Xevertheless, the autlientic specimens which have 

 served either for the establishment of species, or for extending our 

 knowledge in regard to them, are preserved in comparatively few in- 

 stitutions. These are the only reliable standards we have to refer 

 to in cases where the synonymy is confused : and as sucli cases are 

 numerous, it is of importance to systematists to know where these 

 standards are preserved and may be consulted for study. In the 

 sequel, therefore, a list is given of all the type and figured specimens 

 belonging to the largest single collection of Bolca fishes whicli at present 

 exists. In tlie following brief historical summary it is hoped that 

 some facts have been brought together relating to the study of this 

 fauna which shall be of service to investigators. 



1. Old Collections, and Early Studies of Bolca Pishes. 



Although the priority of the Italian school of geology and palaeon- 

 tology amongst those of other nations is clearly established, the share 

 contributed by fossil vertebrates towards stimulating inquiry has been 

 less general]}- appreciated. Fur this reason it may be profitable to cast 

 a retrospective glance over the formative period of these branches of 



