440 CLASSIFICATION OF DEVONIAN FISHES 
Thus, leaving open the question as to the identity of Ce/acanthus 
with Undina, and also that whether Uronemus and Hoplopygus 
(which I have not seen, and concerning which no details are given 
by Agassiz) are Ceelacanths, or not; it appears to be certain that 
fishes closely allied to Caelacanthus granulatus, and known under 
the generic appellations of Uudina and Macropoma, form an exceed- 
ingly well-defined family, to which the term C@ELACANTHINI may 
with propriety be restricted, and which has ranged in time, with 
remarkably little change, from at least as early as the Permian 
formation to the Chalk, inclusive. 
The Ccelacanthini, as thus understood, are no less distinctly sepa- 
rated from other fishes than they are closely united to one another, 
In the form and arrangement of their fins; the structure of the 
tail and that of the cranium ; the form and number of the jugular 
plates; the dentition; the dorsal interspinous bones; the pelvic 
bones ; the ossified air bladder ; the Ccelacanthini differ widely from 
either the Saurodipterini, the Glyptodipterini, or the Ctenododipte- 
rini; but, on the other hand, they agree with these families and 
differ from almost all other fishes, in the same respects as those in 
which the several families just mentioned, have been shown to agree 
with one another ; viz., the number of the dorsal fins, the lobation 
of the paired fins, the absence of branchiostegal rays, and their 
replacement by jugular bones. 
Their special affinities among these three families appear to me 
to lie chiefly with the Ctenododipterini: the scales, the arrangement 
below the second dorsal fin, with which it corresponds in form and structure, but contains 
many more rays. The ventral fins are mutilated, but their position below the first dorsal fin 
is indicated by the preservation of a pair of strong T-shaped pelvic bones, having their 
longer limbs directed forwards, and nearly reaching the base of the pectoral fins. The 
caudal fin is of great size, and presents in an eminent degree the most special and 
characteristic feature of the CaJ/acanthus family, namely, the interposition, in the caudal 
region, of an interneural between the neural and dermo-neural spines. The base of this 
spine abuts upon the extremity of the neural spine, and unites with the true fin-ray by an 
overlap or splice. This structure coincides with that observed in Uudina. In Alacropoma 
the bone of the interneural spine is bifurcate for the reception of the distal extremity of the 
neurapophysis. A small supplemental fin extends an inch beyond the larger caudal fin, as in 
Undina and Calacanthus. The notochord is unossified. The apophyses, both above and 
below, have very wide bases. The scales are curvilinear, and covered with a vermiculate 
pattern on the upper surface, occasionally broken up into small tubercles. 
In the Woodwardian Museum at Cambridge there is the head and part of the trunk of a 
Cwlacanthus, from the Kimmeridge Clay at Cottenham. The head shows the frontals, 
prefrontals, and lower jaw, with the tympanic attachments. The glossohyal plate.is double, 
asin Holoptychius. The scales are roughly undulate, coarser in pattern than in Undzua, 
Calacanthus, and Holophagus, but not absolutely tuberculate, as in AZacropoma. One fin is 
preserved, probably the left pectoral. It is lobate, broad and strong. The operculum is 
triangular, the frontals short, and the prefrontals descend at an abrupt inclination. 
