REPORT OP THE DIRECTOR 1898 r33 



Corrections were made in the horizon of the fossils, and addi- 

 tional information was given whenever possible. We can safely 

 infer the horizon when the locality is known and the fossil in 

 question has been determined. Mistakes in the horizon of the 

 fossils had been made in a great many instances. For example, in 

 the British Tertiary all the specimens from Barton were labeled 

 Middle Eocene. As only beds of Upper Eocene age occur at 

 Barton, the correction from Middle to Upper Eocene was made. 

 Many forms marked Upper Eocene are Oligocene, and this change 

 was made and the Oligocene specimens placed in a separate divi- 

 sion. In the same way, a number of forms marked Upper Eocene 

 were transferred to Lower Eocene. This task was made possible 

 and was much simplified by the use of Prof. Richard B. IN'ewton's 

 excellent memoir on the Oligocene and Eocene Molhisca. This re- 

 port forms one of the special publications of the British museum, 

 and was issued in 1891. 



The classification of British strata adopted is the one given by 

 Sir Archibald Geikie in his Textbook of geology (edition of 1893). 



The marked changes in the nomenclature of the Molhisca have 

 resulted from a more thorough and exhaustive study of this group 

 during the last few years. This study has necessitated alterations 

 and in many cases rejections of generic and specific terms which 

 were applied some twenty years ago. According to the so-called 

 " law of priority," the earliest name of any organism has preference 

 over any later and perhaps more generally used term. The pre- 

 occupation, however, of some of the molluscan names by organisms 

 belonging to other groups, Yermes, Insecta, etc. has necessitated a 

 rejection of several well-known and largely used generic terms. 



Among the more important changes recently made in Lamelli- 

 branchiata for the above reason are the following : 



The name Glycimeris must be used in place of Panopaea- 

 for the former was applied in 1753 by Klein to a bivalve shell 

 identical generically with one from the Pliocene of northern Italy, 

 whereas the Italian fossil was not named Panopaea till 1807 by 

 Menard de la Groye. 



The genus Pectunculus, applied by Lamarck in 1799, must 

 be discontinued, and the term A x i n a e a used in its place, as the 

 latter was given in 1795 by Poll for a similar shell. 



