WHITE OR CORALLINE CRAG. 
199 
the palaeontologist in deciding which sjiecies belong several¬ 
ly to each group. 
Mr. Searles Wood estimates the total number of marine 
testaceous mollusca of the Coralline Crag at 350, of which 
110 are not known as living, being in the proportion of 
thirty-one per cent, extinct. No less than 130 species of bry- 
ozoa have been found in the Coralline Crag, and some be¬ 
long to genera unknown in the living creation, and of a very 
peculiar structure; as, for example, that represented in the 
annexed figure (127), which is one of several species having 
Fascicularia aurantiwm^ Milne Edwards. Family, Tuhuliporidce, of same author. 
Bryozoan of extinct genus, from the inferior or Coralline Crag, Suifolk. 
a. Exterior. &. Vertical section of interior, c. Portion of exterior magnified, d. Por¬ 
tion of interior magnified, showing that it is made up of long, thin, straight 
tubes, united in conical bundles. 
a globular form. Among the testacea the genus Astarte (see 
Fig. 128) is largely represented, no less than fourteen species 
Fig. 128. 
Astarte Omalii, Laj.; species common to Upper and Lower Crag. 
being known, and many of these being rich in individuals. 
There is an absence of genera peculiar to hot climates, such 
as Oonus, Oliva^ Fascioldria^ Crassatella^ and others. The 
absence also of large cowries {Cyprea)^ those found belong- 
