to the same genus as the Batrachians of the Warwick Sandstones,
and, therefore, I shall hereafter describe the German species
under the name of Labyrinthodon Jaegeri.
As the circumstances which led me to detect this generic identity
strikingly illustrate the value of the microscopic structure of teeth
as a distinctive and available test of the nature and affinities of an
extinct species, expecially in the absence of any other character, I
shall here premise the account of these investigations as communicated
by me to the Geological Society of London. (1)
A question was at issue whether the light coloured sandstone of
Warwick was the equivalent of the Keuper or the Bunter division of
the New-Red Sandstone formation as developed in Germany, and its
decision had been set by one of the contending geologists upon the
issue of organic remains, more especially of the supposed Saurian
fossils of the strata in question. “ If it could be shown,” said the
able supporter of the ‘ Bunter’ theory, “ that the fossils which we
have pointed out as characterizing the upper sandstone occurred also
in the lower, and that the fragments of Saurians formed in the
sandstone of Guy’s Cliff and Warwick really belonged to the species
peculiar to the Keuper, then, indeed, we should willingly allow that
the lower sandstone also must be grouped with that formation.”
“ In respect to the Saurian of Guy’s Cliff, which we have had
no opportunity of examining, it is sufficient to state, that Dr. Buck-
land himself does not contend that it is either of the species of the
Phytosaurus (Jaeger) of the German Keuper; and he hesitates even
to refer it to that genus. Now the mere existence of a Saurian in the
Warwick sandstone proves nothing; for Geologists are well aware
that various species of the family occur in all the formations, from the
lias down to the magnesian lime-stone inclusive.”(2)
The reptilian remains figured by the authors above quoted from
the lower or Warwick sandstone were a few teeth or rather fragments
of teeth, and a portion of a vertebra : and these were the fossils to
be compared with the reptiles peculiar to the German Keuper.
(1) Proceedings of the Geological Society, January 20th, 1841. No. 74, p. 257.
(2) “ On the Upper Formations of the New Red Sandstone System in Gloucestershire, Worcestershire
and Warwickshire, &c., by R. I . Murchison, Esq. V.P. G.S., and H. E. Strickland,
Esq., F.G.S.”—Geological Transactions, vol. v, 2d Series, p.p. 345, 346, PI. 28 and 29.
Of such reptiles the least ambiguous and most characteristic remains
were the occipital bone of the Salamandroides giganteus of Prof.
Jaeger: and the teeth of the so called Mastodonsaurus and Phytosaurus.
On the other hand, the reptilian remains of the Warwick
sandstone were still more meagre: no portion of the skull
whereby their batrachian character could be tested was then known ;
the vertebra, as figured in the Memoir cited, apparently presented the
characters of those of the Saurian reptiles(1) ; and the teeth, therefore,
appeared to be the only fossils on which any comparison likely to solve
the question of the relationship between the reptiles of the German
Keuper and of the Warwick sandstone could be founded.
Now it has been seen that the teeth of the Mastodonsaurus are of
a simple and common form ; that they are far from possessing those
well-marked external characters whereby the anatomist can distinguish
the teeth of the Iguanodon, Megalosaurus or Pleiosaurus.
Of the teeth which had been discovered in the Warwick sandstone,
the specimen figured in Messrs. Murchison and Strickland s Memoir,
and which was transmitted to me for examination together with
a similar but larger tooth, most nearly resembled the teeth of the
Mastodonsaurus, in its conical figure and longitudinal striation; but
as these were the commonest characters of Saurian teeth no weight
could be attached to them as proving a specific or generic identity,
bearing upon a geological problem of so much nicety as the one
which related to the Warwick sandstones.
There only remained, therefore, to resort to the test of the intimate
structure of the teeth in question, and upon application to Pi of.
Jaeger of Stuttgard, I was favoured with some portions of the teeth
of the Mastodonsaurus Jaegeri from which were prepared transverse
and longitudinal sections for microscopical examination.
Hitherto in investigating the intimate texture of the teeth of the
Saurian reptiles, as the Crocodile, Plesiosaur, Megalosaur, Monitor,
and most recent Lacertians, I had found the dentine or body of the
tooth to consist of the finest calcigerous tubes, radiating according to
the usual law, from the pulp-cavity, at right angles to the external surface
of the tooth, which is covered by a simple investment of enamel;
(1) Subsequent examination has proved this vertebra to have a concave articular surface
at both ends Qf the body, and to agree in other characters with the Salamandroid type.