WELLBURN : OX THE GENUS CGELACANTHUS. 
477 
advance of these is a large robust azygous element, which probably 
represents the coalesced vomers. Its surface is covered with numerous 
small tubercules, which form a dense rasp-like surface. (This is 
well seen in one specimen in the author's collection.) 
Dentition. — One detached sphenial bone shows on its upper 
border a few irregularly arranged, detached, low, blunt, ill-defined 
elevations, which may possibly have had a dentary function, but 
Avith the exception of the rasps of granules mentioned above, the 
writer has seen no evidence of teeth in these fishes, and he considers 
it to be highly probable that these rasp-like surfaces constituted 
their dentition, at any rate in the Coal Measure species. 
Ceratohyals. — These were robust and connected on each 
side to the hyomandibular by elongated elements, which probably 
represent the stylohyals. 
Branchial Arches. — There are about five on each side, which 
are delicately and deeply channelled on the hinder aspect, as in 
Polypterus. Each arch consists of a pair of much arcuated elements, 
whilst a single large copula, with a spatulate hinder extremity, unites 
all the lower extremities of the arches in the median line. 
Axial Skeleton. — The axial skeleton extends beyond the caudal 
fin to form a supplemental caudal fin. The notochord must have 
been persistent, as its situation is always — so far as the writer has 
seen — represented by a blank space. Reis,"^ however, mentions 
hypocentra as occurring in C. hassice. The neural arches are slender, 
and the two halves of each arch are firmly joined to the neural spines, 
which are long and slender. The lijemal arches are similar to the 
neural, but in the abdominal region their appended spines are short 
and rudimentary, whilst posteriorily, in the caudal region, they 
correspond in development to the neural spines. 
Body. 
The body is covered with deeply overlapping cycloidal scales, 
the exposed posterior portion of which being ornamented with 
ganoine, w^hilst the anterior covered portion is smooth, and shows 
fine concentric lines of grotli, 
* Die Ccelacanthinen — Paloeontograpliica, Vol. XXXV., 1888. 
