TURRILITE. 
3G,9 
It is remarkable that those approximations 
the structure of Ammonites which are pre- 
sented by Scaphites and Hamites, should have 
appeared but very rarely, and this in the lias 
and inferior oolite,* until the period of the cre- 
taceous formations, when the entire type of the 
ancient and long continued genus Ammonite was 
about to become extinct. 
Turrilite. 
t 
The last genus I shall mention, allied to the 
lainily of Ammonites, is composed of spiral shells, 
another form, coiled around themselves in the 
lerin of a winding tower, gradually diminishing 
towards the apex (PI. 44, Fig. 14).t 
The same essential characters and functions 
pervade the Turrilites, wliich we have been trac- 
aig in the Scaphites, Hamites, Baculites, and 
Ammonites. In each of these genera it is the 
Exterior form of the shell that is principally 
* The Scaphites bifurcatus occurs in the Lias of Wurtemburg, 
'^•'4 Hamites annulatus in the Inferior oolite of France. 
+ Tile shells of the Turrilites are extremely thin, and their 
Exterior is adorned and strengthened (like that of Ammonites), 
"'ah ribs and tubercles. In all other respects also, except the 
Planner in which they are coiled up, they resemble Ammonites ; 
interior being divided into numerous chambers by trans- 
"f'se plates, which are foliated at their edges, and pierced by a 
'Phiincle, near the dorsal margin. (PL 44, Fig. 14, a, a.) The 
’4er chamber is large. 
G. 
B B 
