THE CARBONIFEROUS PERIOD. 187 
with lobed or angulated septa, and a dorsally-placed siphuncle 
(situated on the convex side of the curved shells), now for the 
first time commences to acquire a considerable prominence. 
The principal representative of this group is the genus Gonia- 
“ites (fig. 129), which commenced its existence in the Upper 
Silurian, is well represented in the De- 
vonian, and attains its maximum here. 
In this genus, the shell is spirally 
curved, the septa are strongly lobed 
or angulated, though not elaborately 
frilled as in the Ammonites, and the 
siphuncle is dorsal. In addition to 
Gonzatites, the shells of true Ammon- 
ates, so Characteristic of the Secondary 
period, have been described by Dr 
Waagen as occurring in the Carbon- 
iferous rocks of India. 
Fig. 129.—Goxiatrtes (Aganides) Fosse. Carboniferous Limestone. 
Coming finally to the Vertebrata, we have in the first place 
to very briefly consider the Carboniferous fiszes. These are 
numerous ; but, with the exception of the still dubious “ Cono- 
donts,” belong wholly to the groups of the Gavzozds and the 
Placoids (including under the former head remains which per- 
haps are truly referable to the group of the Dipnoi or Mud- 
fishes). Amongst the Gavoids, the singular buckler-headed 
fishes of the Upper Silurian and Devonian ( Cephalaspid@) have 
