34 ON BROCCHI’S COLLECTION OF SUBAPENNINE SHELLS. 
shallow-water conditions and is characterized by its abundance of 
siliceous sponges. 
2. That not the slightest difference can be detected by the most. 
critical conchologist between any of the fossil species in the Pliocene 
formation which are now known to be living and their surviving 
descendants, although an incalculably long period of time must have 
elapsed. These species are extremely numerous, and exhibit varietal 
and abnormal forms of a precisely similar kind in the same fossil 
and living species. 
Discussion. 
The Prestpenrt remarked on the value of this revision by Dr. 
Gwyn Jeffreys of the type collection of Brocchi. 
Mr. J. Starxie Garpner said that it would be of great advan- 
tage if a conchologist with the extensive knowledge of recent forms 
possessed by Dr. Gwyn Jeffreys could undertake the examination 
of the Eocene Mollusca. 
The AvrHor thought that the Eocene Mollusca were almost 
totally different from the recent forms, and he doubted whether there 
was one species common even to the Kocene and Pliocene. 
