592 PROF. H. G@. SEELEY ON THE DINOSAURIA OF 
That brief memoir clearly sets forth the leading characteristics of 
an armoured genus which is well represented at Cambridge. It 
may, perhaps, have been that other Dinosaurs were protected by 
armour undistinguishable from that of Acanthopholis, and that some 
of the Cambridge Dinosaurs were not weighted with these dermal 
plates. There is, I think, evidence to show that the plates were 
arranged in some of these species in one median row placed over 
the neural spines of the vertebrae, with lateral rows of plates, which 
I infer to have been relatively few and large, and placed somewhat 
alter the manner of the scutes of a Crocodile*, but in the tail and 
limbs to have conformed to the plan of the land Chelonia. 
As doubts have from time to time been expressed as to whether 
some of the fossils of the Cambridge Greensand might not have been 
derived from the waste of underlying deposits during its accumu- 
lation, and consequent uncertainty has been freely expressed by 
some writers as to the possibility of bones collected from day to day 
being naturally associated portions of the remains of one animal, it 
may perhaps here be useful to state once for all what the evidence 
is upon which the association of these vertebrate fossils is accepted 
as a basis for specific and generic characters. Almost every phos- 
phatite digging presents fossils with a mineral character peculiar to 
the locality, so that a trained observer who has carefully watched 
these workings for years finds it possible to identify the localities 
of many specimens on this evidence almost with certainty; and 
the chances of imposition by wilful deception are small. Then, in the 
cases of some Plesiosaurs and Ichthyosaurs, I have been present at 
the workings when associated portions of skeletons have been found, 
so that I can state from my own knowledge that naturally associ- 
ated portions of single animals are met with; and often we have 
had to wait for months for the neck of an animal of which the body 
has been found, until the overlying rock was removed so that the 
bones could be collected. The circumstance that private collectors 
rarely obtain associated sets of bones is explained by the necessity 
of being on the spot and watching the workings several times a day, 
so as first to obtain the bones direct from the diggers, and, secondly, 
to obtain any that the diggers may have overlooked, after the phos- 
phatic nodules have been washed in the mills, when the fossils are 
detected if they are strong enough to resist attrition. For a long time 
associated series were limited to portions of one region of the body, 
because the collector was content with the produce of a single washing; 
and it was not until Mr. William Farren employed Mr. Pond, an 
experienced foreman of phosphatite-washers, to devote his whole time 
to visiting the phosphatite-washings about Cambridge, with the 
purpose of collecting the whole of the fossil Vertebrata, that it was 
proved that the bulk of the remains occur as naturally associated 
* A brief account of some 376 Dinosaurian bones from the Cambridge 
Greensand is given in my ‘ Index to Fossil Remains of Aves, Ornithosauria, 
and Reptilia,’ 1869, pp. xvii, 18-24. The bulk of the remains were then 
referred to three new species of Acanthopholis; and since that date the Macru- 
yosaurus semmus has been described and figured in the Journal of this Society. 
