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Proceedings. : : 17 
particularly favourable to the existence of life, and was doubt- 
less one of the causes of the appearance at this time of such a 
varied and important group of organisms.” 
Dr. Hicks has divided the series into two divisions : 
Lower Tremadoc, 200 ft. of dark earthy slates and flaggy 
sandstones, with Neseuretus, Niobe. 
Upper Tremadoc, 800 ft. of iron-stained slates and flags, 
with Asaphus Homfrayi and Angelina Sedgwickit. 
These divisions are not the equivalents of the Lower and 
Upper Tremadoc of Salter and Belt in North Wales, but only 
of their Lower Tremadoc division; and Dr. Hicks thinks that 
“it is not unlikely that the lower portion of the Tremadoc 
Slates at St. David’s was deposited contemporaneously with 
the black beds of the Lingula Flags of N. Wales, as in both 
cases they are the first indications of a change taking place 
in the sea-bottom, after the long period of the shallow sea, in 
which so many thousand feet of Lingula Flags and sandstones 
were deposited.” 
The following are the most important fossils which have 
been found :— 
Neseuretus, 5 species. 
Niobe menapiensis, Hicks. 
»  8olvensis, Hicks. 
Dendrocrinus cambrensis. 
Palasterina ramseyensis, Hicks. 
Ctenodonta, 2 species. 
Modiolopsis. 
Orthis Carausii, Salter. 
»  menapiz, Hicks. 
Asaphellus Homfrayi and Ogygia scutatrix were also found by 
Dr. Hicks at St. David’s, but he found them associated with 
graptolites of Arenig age. We have seen that in N. Wales 
they are recorded from the Upper Tremadoc beds. This has 
led Dr. Hicks to the view that his Lower Arenig beds of 
S. Wales are represented by the Upper Tremadoc of N. Wales. 
Tf this view were correct, and it is supported by one or two 
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