Geological Society of London. 111 
hailed with pleasure by students of cretaceous beds all over 
Kurope. The portion published embraces the Belemnites, 
the Nautili, and part of the Ammonites, and contains descrip- 
‘tions and figures of 24 species, of which two are wholly new, 
and six new to British lists. The range of cretaceous strata 
from whence the specimens described have been procured, 
extends from the Upper Chalk of Norfolk and Gravesend, to 
the Chloritic marl of the Isle of Wight, and “ Chalk with 
green grains” of Somersetshire. It is worthy of notice that 
of the Nautili described, several are recorded as having 
an extensive vertical distribution ; thus Nautilus levigatus 
ranges from the Upper Greensand to the Upper Chalk, whilst 
Nautilus pseudo-elegans, N. radiatus, N. neocomiensis, and 
NV. undulatus occur in both the upper and lower divisions of 
the Cretaceous system ; in other words, both above and be- 
low the Gault. Every fact of this kind well ascertained, is 
of no small interest at present, when there is an extreme and 
unwholesome tendency on the part of many paleontologists 
to insist @ priori upon the distinctness of species coming 
from different stages, and to force their diagnoses ‘accord- 
ingly... 
The essay on the classification of the Brachiopoda, by Mr 
Davidson, contains the conclusions arrived at after many 
years of conscientious labour, mainly devoted to this in- 
teresting order of Mollusks, for whose illustration we owe 
so much to his pen and pencil. No other palzontologist has 
ever had so great an amount of perfect materials for his par- 
- ticular task at his command, and neither expense nor labour 
has been spared by our indefatigable associate to render his 
monograph as perfect as possible. If any of our brethren 
dissent from some of his specific decisions, they must all 
admit that they have been arrived at on no superficial 
grounds. The portion of Mr Davidson’s work now sent forth 
is entirely systematic, and is devoted chiefly to an exposi- 
tion of the characters and definition of the families and 
genera of Brachiopoda. He admits thirty-three genera as- 
sembled under ten principal families, with some intermediate 
and doubtful or provisional groups. As he has endeavoured 
to define his genera on the strictest natural characters, and 
appears to have succeeded in arriving at an arrangement, 
