210 
REVIEW OF THE PERMIAN FOSSILS. 
paucity of species to make us presume, that the causes which were opposed to their 
free development produced very extensive effects. 
The Cephalopods, which under the forms of Goniatites, Nautilus and Ortho- 
ceras were so numerous during the Carboniferous period, that 160 species have 
been already described from its strata, were almost entirely annihilated previous to 
or at the commencement of the Permian eera. At all events, notwithstanding 
our keen researches, we have been unable to obtain the smallest trace of a Go- 
niatite or Orthoceratite in any of the Permian tracts of Russia, the only specimen 
of Cephalopod which we could detect being a fragment of a doubtful Cyrtoceras, in 
the limestone of Shidrova, near Ust-Vaga. A Nautilus, figured by Dr. Geinitz 1 , 
is the only specimen of a Cephalopod with which we are acquainted in the Zechstein 
of Germany. The museum of the Natural History Society of Newcastle possesses 
also some fragments of a Nautilus, to which Mr. King refers the portions of a 
chambered shell, assigned to an ammonite by Professor Sedgwick, in his Memoir 
on the Magnesian Limestone. Now if the chambered fragments which we found 
in Russia, and supposed to belong to a Cyrtoceras, should prove to be portions of a 
Nautilus, the Cephalopods are reduced to a solitary genus of very rare occurrence. 
This scarcity of Cephalopods at the close of the Palseozoic sera has a remarkable 
parallel in a subsequent geological period ; for as these animals were reproduced in 
vast abundance and under many new forms in the Triassic, Jurassic 2 , and Creta- 
ceous systems, so towards the termination of the last of these, w T e perceive a 
second and similar disappearance of the greater number of shelly Cephalopods. 
The extreme reduction in the number of Gastropods at the close of the Cretaceous 
period is, indeed, an additional feature of resemblance between these two epochs ; 
for twenty-four species of this class only have been discovered by M. d’Orbigny in 
1 Neues Jahrbuch, Leonhard, 1841, pi. 11. f. 1. Whilst we write Professor Sedgwick has discovered 
a Nautilus in the Lower Silurian rocks of Bala in North Wales, and thus Cephalopods of this generic 
form, have existed from the older Palseozoic or Protozoic to the present period, however they may have 
been obliterated at certain epochs. 
a The recent researches of M. Alcide D’Orbigny have led him to believe, that the close of the Jurassic 
period bears a strong analogy to the termination of the Palaeozoic and Cretaceous aeras in the notable 
diminution of the number of chambered shells. In the Portland rock he admits hut three species of 
Ammonites, which certainly seem to be of small value when contrasted with the prodigious numbers of 
species of these creatures on the one hand in the lias, lower and middle oolite, and on the other in the 
succeeding greensand and cretaceous rocks. English geologists, however, cannot forget that in the 
frequent occurrence of the same species and in the extraordinary size of the individuals, the Portland rock 
is eminently Ammonitic. 
