392 
' DR. MANTELL ON THE HYL.EOSAURUS. 
be identical with that of the dermal scutes of the Hylaeosaurus, presenting ‘Hong, 
straight, spicular fibres, decussating each other in all directions, and representing, as 
it seems, the ossified ligamentous fibres of the original corium*.” 
At length, after the lapse of eighteen years, I have obtained one of these spines in 
which the proximal end or base is sufliciently entire to show the nature of its con- 
nection with the body of the reptile. This specimen (for which I am indebted to the 
liberality of Mr. Peter Fuller of Lewes) was found a few weeks since in the same 
quarry in Tilgate Forest, whence the first discovered skeleton of the Hylseosaurus 
was obtained ; and there is reason to conclude that it may have belonged to the same 
individual, for several detached dermal scutes and spines of corresponding size and 
character, have from time to time been found in the sandstone near the spot. 
This spine, if perfect, would be 15 inches in length ; its base or proximal end is of 
an elliptical form, with a longitudinal median depression, which is bordered by a 
gentle rounded eminence ; the articulating surface has the corrugated aspect that 
characterizes the ossified dermal scutes of the Hylaeosaurus ; and a comparison of the 
base of this spine with that of the unquestionable dermal bones, confirms the correct- 
ness of my original interpretation of the nature of these remarkable processes. 
In the accompanying drawings the characters of the original are sufficiently de- 
fined, to render further description unnecessary. 
This fact is of considerable interest, since it demonstrates in the dermal system of 
the extinct colossal Saurians of the secondary geological seras, a similar exaggerated 
development to that which prevails in the living diminutive representatives ; but while 
in the existing Lizards the dermal appendages are flexible and cartilaginous, in the 
fossil reptiles they are rigid osseous spines ; the difference arising from the ossifica- 
tion of the ligamentous fibres of the coriuni in the dermal bones and spines of the 
Hyleeosaurus. 
Description of the Plate. 
PLATE XXVII. 
Fig. 1. Lateral view of the dorsal dermal spine of the Hylseosaurus ; reduced to one- 
half linear. 
Fig. 2. View of the articulating surface of the base. 
Fig. 3. Magnified view of a portion of the internal structure, showing the decussating 
ossified fibres of the corium, the bone-cells, and the Haversian canals, as 
exposed in a section seen by transmitted light. 
Chester Square, Pimlico, 
June 1850. 
* See Wonders of Geology, 6th edition, p. 437. 
