Review of Recent Geological Literature. <>1 
birds; all traces of reptilian affinities having been lost in this order. 
The order is treated under a great number of families, only a few of 
which are of palaeontologieal importance. The siluroids have suggested 
to Prof. Huxley by several points of resemblance a near relationship to 
the ganoids. But a difficulty occurs in the fact that they are not known 
with certainty before the Tertiary era. Of especial interest is the 
family of the horse-mackerels (Carangidse) on account of the excellent 
preservation of its fossil specimen in the Monte Bolca Eocene of north- 
ern Italy, a series of limestones associated with volcanic material which 
has yielded to the labors of Agassiz 133 species of fish represented by 
immense numbers of specimens. Of the flat fishes we have almost no 
fossil remains, only two genera, the turbot and sole, being known. 
The introduction of the teleostean fish is of very recent date, none of 
them having been found fossil in rocks older than the Cretaceous. They 
are essentially Tertiary in date, but have advanced so rapidly in num- 
ber of species and of individuals that they form to-day a very la rue 
majority of the existing fishes of the globe. 
The Amphibia are a class of very great interest to the palaeontologist 
as they form a transition group between fishes and reptiles. The sur- 
vival of this class to the present day has enabled the evolutionist to 
bridge over a chasm which would otherwise have existed between these 
groups. Of the whole class, however, only one order, the labyrintho- 
donts, is geologically ancient. Of the Apoda no fossil remains are 
known, while the salamanders, frogs, and toads are only found in later 
Tertiary strata. This leaves an enormous gap in the geological history 
of the class, the latest known labyrinthodonts being found in the Trias 
and the earliest of the other orders in the Tertiary or possibly and 
doubtfully in the Cretaceous. They are especially characteristic of the 
latest part of the palaeozoic era and of the earlier Mesozoic ages. From 
the Carboniferous to the Trias in Europe and North America their re- 
mains occur, but only a single genus, says Mr. Lydekker, ascends to 
the Lower Jurassic-. Their remarkable and complicated tooth-structure 
from which the name is derived characterizes the greater part of the 
order, though iu a few this feature is wanting. 
In this connection we may note the fact that not a few of the laby- 
rinthodonts were first known by their footprints in double series with a 
small fore and a large hind track. Chelroiherbum, or rather Cheiro- 
saurus, was the earliest of these in date of discovery, but the records of 
this kind drawn from the sandstones of the Connecticut valley by the 
labors of the Messrs. Hitchcock, have surpassed all found elsewhere. 
and unmistakably prove an abundance of labyrinthodont and other life 
in the Trias. Thousands of these footprints have been extracted from 
the quarries and (ens of thousands more have been destroyed. 
The gap above alluded to in the history of t he Amphibia would lead 
us to seek the origin of the class of reptiles in the labyri nt hodouts. for 
undoubted members of this group appear as early as the Permian and 
possibly in Carboniferous days. Bui the teeth of true reptiles never 
