CffiLACAXTHIDJE. 
397 
neural arches and spines are long and slender, the two halves of 
each arch being firmly united with their appended spine. In the 
abdominal region, the haemal arches are delicate and rudimentary, 
hut in the caudal region they correspond in development to the 
opposed neural elements. So far as known, these ossifications 
extend only to the termination of the principal caudal fin, the 
small supplementary caudal never displaying hard endoskeletal 
structures. 
The paired fins are always well-developed and obtusely lobate. 
The membrane-bones of the pectoral arch, though slender, are con¬ 
spicuous, and seem to have been completely covered by the skin. The 
long, gently curved clavicle often exhibits a robust post-clavicular 
process, and articulates above with a small supraclavicle ; while a 
long, slender infraclavicle overlaps its lower spatulate extremity. 
The last-mentioned element curves sharply forwards and inwards, 
terminating in a triangular expansion, where it meets its fellow of 
the opposite side in a median suture (see PI. XIY. fig. 3, i. cl.). The 
pelvic fins are supported by a pair of elongated, slender basipterygia 
with an inwardly directed process at the distal end, by which they 
are loosely apposed in the median line. 
Of the two dorsal fins, the anterior is destitute of baseosts, the 
stout dermal rays directly articulating with the nearly straight 
upper border of the single laminar axonost. This fin therefore 
exhibits no lobation. The posterior dorsal fin and the opposed anal 
resemble the paired fins in being distinctly lobate. As in the paired 
fins, the baseosts must have been too slightly ossified for preservation, 
the lobe being always a vacant space in the fossils ; but there is a single 
forked axonost to each fin, this almost invariably exhibiting a high 
degree of ossification. The principal caudal fin is symmetrical, and 
supported by a single series of long slender bones above and below, 
equalling in number, and directly apposed to, the blunt distal 
extremities of the neural and haemal spines of the axial skeleton. 
A single stout dermal ray is connected with each of these elements 
by a simple overlapping^articulation ; and a sparse series of very 
small rays fringing the supplementary caudal lobe, when present, is 
probably in direct contact with the unossified spines of the axial 
skeleton itself. Xone of the fin-rays are bifurcated, but all are 
more or less articulated distally. 
A conspicuous feature in the abdominal region of all Coelacanths 
is the ossified air-bladder, which attains a large size, and sometimes 
exhibits a single anterior aperture by which its internal cavity 
communicated with the oesophagus. Its walls are formed of three 
paired longitudinal series of large, imbricating, bony laminae, each 
