154 _ CTENACANTHUS, A SPINE OF HYBODUS. 
b 
covered accompanying Hybodus spines or teeth in the Wealden 
or Lias I do not know, but even if they have never drone found so 
associated in rohan formation s my view would not receive any 
confutation, for in order that these light fuberelie should be 
deposited in close proximity to such heavy objects as spines and 
teeth the water would have to be in perfect quiescence, and then 
in the character of the fish itself might have undergone 
change in this respect during the mighty ages which passed away , 
between the Carboniferous and the Jurassic periods. 
Both the spines and teeth of Hybodus from the Coal Measures 
have been found buried in or associated with masses of shagreen 
and disintegrated cartilage. 
ichwald, a — paleontologist, after an ery eh of some 
ines found in arboniferous Limestone of Russia, came to 
oe, conclusion that they belonged to Hybo sing and named them 
accordingly H. panderi. He also asserts, in his “Lethaa Rossica,” 
that H. polyprion of Agassiz has been discovered in the same 
formation. 
To sum up: all the deductions and descriptions drawn out b 
' Agassiz and neg vit base gt to ee a the more recent 
formations can be a with equal t o the spines of 
Hybodus (Ctenaeanths and i the teeth af "Sytodue (Cladodus) 
from the Coal Measures; the only statement requiring correction 
i i siles’:—* Les H 
c’est-a-dire jusqu’aux derniers dépéts jurassiques et weldiens ; 
ils existent méme dans la Craie.” This will require the substitu- 
tion of “vieux grés-ro a for “ grés-bigarré,” for although 
this paper is directed pee to the Coal agen remains, 
undisputed spines of Hybodus (Ctenacanthus) are found in the 
Carboniferous Limestone and in the Old Red Sandstone. In 
these latter formations teeth of poe are also ge red, 
but not nea of Hybodus, so far as 1 am aware. This, however, 
is of no importance, because it is ebanl that the fish Cladodus 
alison spines exactly similar to Hybodus, if Cladodus be not 
equal in number a ak side | of the central cone ; while 
ybodus they decrease in size and may be equal or Benes 
each side. Now, I have examined specimens of Hybodus having 
all the secon i i 
they were all the same height a the centre denticle and equal in 
