J 
DEVONIAN AND OLD RED PERIOD. 149 
(fig. 100). The latter, with its fragile, conical, and often beauti- 
fully ornamented shell, is especially noticeable. 
The remains of Cephalopoda are far from uncommon in the 
Devonian deposits, all the known forms 
being still Tetrabranchiate. Besides the 
ancient types Orthoceras and Cyrtoceras, 
we have now a predominance of the 
spirally-coiled chambered shells of Gove- 
atites and Clymenia. In the former of 
these the shell is shaped like that of the 
Nautilus ; but the partitions between the 
chambers (“septa”) are more or less 
lobed, folded, or angulated, and the 
‘‘ siphuncle” runs along the dack or con- 
vex side of the shell—these being char- 
acters which approximate Govnzatites to 
the true Ammonites of the later rocks. 
In Clymenia, on the other hand, whilst 
the shell (fig. ror) is coiled into a flat 
spiral, and the partitions or septa are 
simple or only slightly lobed, there is still 
Fig. 1co.—Conzularia or- 
nata, of the natural size. 
Devonian, Europe. 
this difference, as compared with the /Vaw7z/us, that the tube of 
the siphuncle is placed on the zwzzer or concave side of the 
Fig. 101.—Clymcenia Sedgwickit. Devonian, Europe. 
shell. The species of Clymenia are exclusively Devonian in 
