JVith the kind permission of Dr. Lloyd, 1 took a thin transparent
transverse section from the middle of the tooth, corresponding with
thepiace of the sectionl from the German tooth above described:
t v fig' 2’ 1S shown the structure of the tooth of the British
Labyrinthodon as seen by transmitted light in one half of the
ransverse section j the complication of the interhlended lamina: of
dentine and cement is as remarkable, and its plan is the same as in
the tooth of the great Labyrinthodon of the German Keuper
All the peculiarities, indeed, of this most extraordinary type of
dental structure are so closely preserved in the specimen from the
Warwick sandstone, that generic identity, at least, may be predicated
ot the tossils from both localities.
The differences which require to be noticed are such as might
e expected in distinct species of the same genus. The inflected folds
of cement in the Warwick tooth are continued for a greater relative
extent before the lateral sinuosities commence, than in the German
reptile, and the inflections or anfractuosities - are rather fewer in
number; some of the inflected converging folds in the Warwick
tooth, having nearly reached the central pulp-cavity, are reflected
backwards for a short distance before they terminate.
The modifications of the complex diverging plates of dentine
correspond with those of the tooth of the Labyrinthodon JaegeriI but
their terminal quadrilateral lobes, as seen in the transverse section
are relatively longer.
The number of the inflected folds of cement is equal to that
m the Lab. Jaegeri and varies in the same degree at different
parts of the tooth; thus the folds which reach longitudinally to
near the apex of the tooth extend inwards to near its centre in
the section figured, and the shorter folds are inflected to a less
extent proportionate to their diminished length.
The dentine is composed of calcigerous tubes of the same
relative size and disposition as in the Labyrinthodon Jaegeri. The
base of the tooth appeared to have been similarly osseous substance of the jaw. anchylosed to. the
After having adduced this evidence of the affinity of the fos-
Si s of the German and British sandstones, I concluded by stating
that the results of the comparison might be deemed to be decisive
as to the existence of reptiles in the latter formation, which belong
to the same natural genus as does one of the most peculiar of the
extinct reptiles of the German Keuper.
So far, therefore, as the geological question, to which reference
was made at the beginning of the present section, depends upon the
determination of the generic identity of the reptilian fossils in these
formations, it must be regarded as supporting the view entertained by
Dr. Buckland of the correspondence of the Warwick and Bromsgrove
sandstones with the Keuper sandstones of Germany. And if, on the
one hand, geology has, in this instance, derived any benefit from
microscopical investigations of animal tissues, on the other hand it
must be admitted that in no instance has comparative anatomy been
more directly indebted to geology than for the fossils, and the
stimulus to their microscopic investigation, by means of which a
knowledge has been obtained of the most beautiful and complicated
modification of dental structure hitherto known, and of which no
adequate conception could have been gained from investigations,
however close and extensive, of the teeth of existing species of animals.
88. Labyrinthodon leptognathus.—When the results of this comparison
of the microscopic structure of the tooth of the Labyrinthodon
Jaegeri and of the smaller tooth of the Warwick sandstone were
communicated to Dr. Lloyd, he transmitted for my inspection all the
fossils from the same stratum which had been deposited in the local
or private museums of Warwick and Leamington, with permission to
apply the microscopic test to any of the teeth which these fossils
might contain. I shall here briefly notice such of these fossils as
throw additional light on the dental characters of the species to which
they belonged.
The most valuable and characteristic fossil in this respect is the
anterior part of one side of the upper jaw, including the nasal
bones (PL 63 a , figs. 1 and 3). It shows that the maxillary or facial
division of the skull was broad, much depressed and flattened,
resembling in this respect the skull of the gigantic salamander and
alligator, and having the outer surface of the hones strongly sculptured
by depressions and furrows as in the crocodilian family.