38 
CORALLINE CRAG. 
small differences as of specific value. Of course if this is the 
case, it would only cause confusion to treat the English Pliocene 
inollusca in a way that none of the continental palaeontologists 
seem inclined to adopt for their Pliocene faunas. Any such 
revision would render it even more difficult than at present to 
compare the deposits, and the change would lead to no useful 
result. The Crag Mollusca ” has therefore here been adopted 
as the standard authority, and Wood’s determinations have only 
been departed from in cases where there is a general concurrence 
of opinion against him, or where further evidence has shown that 
errors have been made. 
It has long been known that a large proportion of the Coralline 
Crag mollusca are of Mediterranean or southern type, and Wood 
in 1874 analysed the list thus :— 
British and not Mediterranean - - 20 
British and Mediterranean - - 154 
Mediterranean and not British » - 51 
Neither British nor Mediterranean - 24 
Not known living - • - - 142 
Total - - 391 
A considerable proportion of the extinct forms, and also of the 
living species that are neither British nor Mediterranean, are 
allied to southern molluscs (see Plates II, and III.) or are found 
in Miocene beds. One species only, according to Wood, is 
exclusively Arctic, and in this case he considers the delermination 
somewhat doubtful. Jeffreys considers that several more of the 
Coralline Crag shells are Arctic. 
However, we may put on one side these critical species, for it 
is evident that a study of the general character of the fauna will 
yield more satisfactory results. The statistical method also leads 
to the absurd position that a certain number of critical species, 
which according to the authority we follow, may be northern, 
southern, or extinct, are considered of equal value with a like 
number of southern species, belonging often to genera now 
unrepresented in northern seas. Among the genera which give 
such a southern character to the Coralline Crag fauna are large 
showy species of Voluta, Cassidaria, Cassis, Ficula, Hinnites, 
Chama, Cardita, and Pholadomya, Equally characteristic are 
the smaller Ovula, Mitra, Triton, Vermetus, Ringicida, Verti- 
cordia, Coralliophaga, and Solecurtus. These do not all belong to 
recent species, but even when the species is extinct, it can 
generally be found in south European Miocene or Pliocene beds, 
associated with a fauna still more southern than that of the 
Coralline Crag. Wood has also pointed out that “ the most 
abundant and therefore most characteristic species of the Coralline 
Crag, such as Cardita corbis, Cardita senilis, Limopsis pygmcea, 
JRingicula huccinea, and others, are southern species unknown to 
British seas, and that among the 154 Coralline Crag species 
occurring both in British and Mediterranean waters there are many 
