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1847.| BOWERBANK ON THE PTERODACTYLUS GIGANTEUS. 7 
radiating from the cells and presenting all the characters of those of 
well-known and characteristic mammals. The fragments from the 
second specimen of T’hylacotherium Prevostii, represented by fig. 1. 
Pl. 5. vol. vi. 2nd Series of Transactions of the Geological Society, 
were not so fortunate in their direction, haying splintered off rather 
obliquely to the axis of the bone, but in other respects they presented 
precisely the same characters as those from the first specimen. ‘They 
are represented at fig. 5. Pl. I. Their average measurement was—— 
length +4 inch, greatest diameter =,,, inch. The canaliculi were 
equally abundant and quite as much attenuated as in the first speci- 
men, and the abundance of the cells within a given space was in per- 
fect accordance with the other mammalian characters; the difference 
in their length from the first specimen being accounted for by the 
oblique position in which they were presented to the eye. 
Mr. Morris also kindly furnished me with a third specimen of a 
small jaw from the Stonesfield slate, which appears to me to be Thy- 
lacotherium Broderipii, and a similar examination of fragments from 
this produced precisely the same results as those recorded of the jaws 
in the possession of Dr. Buckland. 
The structural peculiarities therefore appear to place the mammalian 
character of these long-disputed remains beyond a reasonable doubt, 
and to confirm the opinion so laboriously and ably worked out by 
Prof. Owen, of their having belonged to true mammals, and in no 
respect being allied to the Reptilia. 
With the jaw from the Stonesfield slate my friend Mr. Morris 
sent me a small vertebra from the same formation, which is represented 
by fig. 6. Pl. II. Small fragments from this bone afforded similar 
results to those from the jaws. The bone-cells represented at fig. 4. 
Pl. I. present all the proportions and appearance of those of mam- 
malian remains, and none of the characteristics of the reptilian tribe. 
The average dimensions of five of these cells were—length ;,,, inch, 
greatest diameter ~4,, inch. 
The Chalk and the Stonesfield slate are not the only strata that 
have produced bones which have been the subject of dispute in the 
geological world. Dr. Mantell, on the 10th of June 1835, read a 
paper before the Geological Society ‘‘On the Bones of Birds disco- 
vered in the Strata of Tilgate Forest in Sussex.’ Doubts had existed 
previously to the publication of this memoir whether the bones which 
are the subject of it were not those of Pterodactyls; but on the high 
authorities, in the first place of Cuvier, and secondly of Professor 
Owen, they were decided to belong to extinct species of wading birds. 
Subsequently the latter great comparative anatomist, it appears, mis- 
trusted this decision, and having re-examined the bones which are 
now deposited in the British Museum, and numbered 453 and 2353, 
he published the result of this fresh examination in a paper read _be- 
fore the Geological Society on the 17th of December 1845, entitled 
“On the supposed Fossil Bones of Birds from the Wealden.” In 
this communication Professor Owen enters at length into his reasons 
for changing his opinion respecting these specimens, and ultimately 
decides upon designating them as remains of Pterodactyls; that is to 
