394 
CROSSOPTERYGII. 
Suborder III. ACTINISTIA. 
Notochord persistent. Axonosts of each of the dorsal and anal 
fins fused into a single piece ; a series of axonosts, equal in number 
to the supporting neural and hrnmal spines, present in the caudal 
fin above and below, each axonost directly connected with a single 
dermal fin-ray. Axonost of pelvic fin on each side single, the right 
and left not fused together mesially. 
Of this suborder only one family, that of the Ccelacanthidm, is 
at present known. 
Family CffiLACANTHIDiE. 
Body deeply and irregularly fusiform, with cycloidal, deeply- 
overlapping scales, more or less ornamented with ganoine. Branchi- 
ostegal apparatus consisting of an operculum on each side and a 
single pair of large jugular plates. Paired fins obtusely lobate. 
Two dorsal fins and a single anal; the anterior dorsaf without 
baseosts, the posterior dorsal aud the anal with baseosts, obtusely 
lobate. Axial skeleton extending to the extremity of the caudal 
fin, usually projecting and terminated by a small supplementary 
caudal fin. Air-bladder ossified. 
As in many other piimitive types of fishes, the arches and spines 
of the axial skeleton in this family are only superficially ossified, 
thus appearing, in the fossilized state, as if originally hollow. Such 
an appearance suggested the name of Ccelacanthidm to Agassiz, 
who used the term in a wide and somewhat indefinite sense. The 
first scientific definition of the family was given by Huxley in 
1861 and 1866. 
The most satisfactory information concerning the osteology of 
the Coelacanthidee is afforded by remains from the Chalk of Eng¬ 
land and the Lithographic Stone of Bavaria. Macropoma, from 
the Chalk, is described in detail by Huxley \ chiefly from specimens 
recorded below; while the genera of the Lithographic Stone are 
elucidated by Peis in a recently published memoir 2 . Undina qulo, 
from the English Lias, is also often well preserved, and a restora¬ 
tion of the skeleton is given in fig. 53, p. 412. 
T. H. Huxley, Illustrations of the Structure of tlie Crossopterygian 
Ganoids ” (Mem. Geol. Surv. dec. xii. 1866). 
O. M. Reis, Die Ccelacanthinen, mit besonderer Beriicksiclitigung der im 
Weissen Jura Bayerns vorkommenden Gattungen” (Pakeontograpliica vol. 
xxxv. 1888). 
