AQ GEOLOGICAL MEMOIRS. 
The Saurtans of the MuscHELKALK (Die Saurier des Muschel- 
kalkes mit Rucksicht auf die Saurier aus buntem Sandstem und 
Keuper: Zur Fauna der Vorwelt, Zweite Abtheilung), by HERMANN 
von Meyer. Ilste Lief. Frankfurt, 1847. Folio. 
Tuts portion of the work contains the first five sheets of the text 
and twelve folio plates. The imtroduction gives an account of the 
trias formation ; followed by a general description of the skull of the 
Nothosaurus figured in plate 1; and specially of the Nothosaurus 
mirabilis, and of the N. Miunsteri, of which figures are also given. 
These remains are from the Muschelkalk of Bayreuth, where they 
were discovered by the well-known Count Minster, who also first 
distinguished them from Plesiosaurus, with which genus they had 
been confounded. This account of the Saurians of the Muschelkalk 
will be continued in other numbers of the work, and will be sue- 
ceeded by similar monographs of the saurians of the keuper and 
bunter sandstone, thus forming a connected view of the whole sau- 
rian world of the trias. The remains are described according to the 
localities where they occur, it not bemg possible as yet to describe 
them systematically according to species, there being many remains 
which could not be assigned to particular species, but yet too im- 
portant to be passed over. The following are some general remarks 
on the trias formation (die Triasgebilde) and the remains of verte- - 
brated animals found im it, from the introductory part of the work. 
As in the living creation we must not only define the species with 
accuracy but also determine their geographical distribution and their 
vertical distance from the surface of the sea, so also in reference to 
fossil begs it 1s necessary to know in what locality they were found 
and to which section in the history of the earth they belong. Geo- 
logy can alone give an account of the latter—of the date of these 
bemgs in the chronology of the world. Hence it is indispensable, in 
a work treating of the saurians of the muschelkalk, to take a review 
of the formation im which their remains are found. It appears that 
the muschelkalk is no independent, isolated formation, but the cen- 
tral member of three formations intimately connected together, the 
representatives of only one period in the history of the earth, and 
hence designated by the name of the Trias. The Councillor of 
Mines, V. Alberti, has proved this most convincingly, though at that 
time the saurian remains of the formation had not been accurately 
examined. I have since been much employed in researches on these 
animals, and the results are highly favourable to this view. The 
three formations are the Bunter sandstein, the Muschelkalk, and 
the Keuper. The remains contained m them belong to saurians, of 
types not previously represented on the earth, and of which only one 
family, the Macrotracheli (in consequence of the occurrence of the 
Plesiosaurus in the lias of England), extends into the followmg geo- 
logical period. It must however be observed in reference to this 
point, that the genus Plesiosaurus has not yet been certainly proved 
to occur in the trias formation, so that the peculiarity of the trias- 
saurians is scarcely affected by the appearance of a related genus in 
the period that mmediately follows. The geological age of the trias 
