CLINTON GROUP. 105 
unequivocal evidence of the existence of vertebrata which we have yet discovered in this 
country. 
There have been found some fragments imbedded in a coarse conglomeritic mass in this 
group, which resemble bones in their structure ; but all these which I have examined prove 
to be inorganic, and to have only a fibrous or porous mineral structure. 
The small fragment now figured has the form as well as the structure of these defensive 
bones ; and though in such a condition that no definite markings appear by which to charac¬ 
terise it, it is nevertheless of sufficient importance to be represented. 
Since this fragment was figured, I have obtained another more perfectly preserved from the 
sandstone in the lower part of the group. This specimen will be represented, with one from the 
Niagara group, on Plate 71. 
Pl. XXXI. Fig. 7. 
The specimen figured has the form and proportions of the rib of some vertebrate animal, 
but it preserves no bony structure, being entirely replaced by siliceous matter. 
This specimen was found in the upper gray sandstone, associated with the preceding fossils of 
Plates 30 and 31. 
[ Palaeontology— Vol. II.] 
14 
