DAVIS : KOTE ON CHLAMYDOSELACHUS. 
109 
have been most carefully and assiduously watched for more than 
twenty years, and if spines of Ctenacanthus had been present they 
would certainly have been collected. Altogether between thirty 
and forty species of fossil fishes, other than those already named, 
have been found in the beds which it is probable belonged to the 
fish Cladodus. Associated with the Ctenacanthus spines at Oreton 
in Salop there are numerous teeth of Orodus, but there is no evidence 
except the fact of their association which would lead to the inference 
that they might have existed together as part of the living fish. 
A remarkable contribution to the knowledge of the genus 
(Ctenacanthus was made by Dr. R. H. Traquair in the Geological 
Magazine (Decadi III., Vol. I., p. 3). He there describes a fossil 
shark from the Lower Cai-boniferous beds of Eskdale in Scotland, now 
in the Natural Histor}^ Museum, London. The length of the fish is 
28 inches and its greatest depth 5 inches : it possesses two dorsal 
spines situated in front of fins which occupy the same relative posit- 
ion as do those of the Hybodus of the Lias. The anterior spine is 
four-and-two-thirds, and the posterior one, four inches in length. 
The verterbal axis and the head were cartilaguous, the latter much 
crushed and not well defined. The only distinctly visible tooth is 
detached from the jaws ; it is one-eig'hth of an inch in length, 
and consists of a single smooth denticle with an expanded base which 
Dr. Traquair considers might support lateral denticles. 
In the Coal Measures, separated from the Carboniferous Lime- 
stone by the Millstone Grit series, in some localities attaining a 
thickness of between one and two thousand feet, the spines of 
Ctenacanthus are almost universally common, and indicate a fish of 
large size ; but teeth of the Cladodont type are rarely found, and in 
some districts are entirely absent. In the Scotch L'pper Coal 
Measures the spines and teeth occur, and have been attributed to about 
an equal number of species of each genus respectively. In the 
Yorkshire coal field three species of Ctenacanthus have been 
determined, but no well-defined teeth of Cladodus have been recorded. 
Teeth have been found which approach to some extent the Cladodont 
type, they have a broadly expanded base with several cones arising 
therefrom, the central one the largest, one-third the length of the 
