108 
DAVIS : NOTE OX CHLAMYDOSELACHUS. 
species described by Dr. Traquair, to be mentioned hereafter, the 
spines of Ctenacantiius have not been found associated with the 
teeth of Cladodus in such close juxtaposition as to render undoubted 
their relationship the one to the other. Both the teeth and the 
spines are found most frequently in the Mountain or Carboniferous 
liimestone Series. They also occur with tolerable frequency in the 
Coal Measures above; and spines of Ctenacanthus, or others very 
similar in foi-m and structure, have been found as low stratigraphically 
as the Upper Silurian rocks. In the latter no teeth have hitherto 
been discovered which can be said even approximately to belong- to 
the same fishes as the spines. From the Mountain Limestone of 
England and Ireland fourteen species of Ctenacanthus have been 
obtained, and from the same beds twelve species of Cladodus. The 
larger number in each case have been collected, principally by the 
indefatig-uable exertions of the Earl of Enniskillen, whose magnificient 
collection now forms part of the National collection at the New 
Natural History Museum in London ; from the limestone quarries in 
the neighbourhood of Armagh in Ireland whence ten species of 
Ctenacanthus and eight species of Cladodus have been obtained; 
from Bristol there exists three species of the latter, whilst at 
Oreton in Salop, four species of Ctenacanthus have been found, three 
of which are the same species as those found at Bristol, but no teeth 
of Cladodus have been discovered. In Yorkshire numerous teeth of 
Cladodus comprised in four species, occur in one of the Yoredale 
Limestones which form one of the uppermost beds of limestone in 
the Carboniferous series, though no trace has hitherto been discov- 
ered of the remains of Ctenacanthus spines. In other districts teeth 
of Cladodus are occasionally found, but the spines of Ctenacanthus 
are not associated with them. Both are found in the Scotch beds. 
A comparison of these facts exposes some peculiarties ; for whilst in 
the limestones of Armagh and Bristol, the relative proportion and 
occurence of the two g-enera is nearly equal, there is the phenomenon 
in the Yorkshire series of four species of Cladodus being in existence 
without spines of Ctenacanthus and vice versa in Salop. It is not 
probable that these pecularities occur in consequence of want of 
investigation, because, in the Yorkshire beds at an^^ rate, the quarries 
