586 SYSTEMATIC RELATIONS OF FISHES. 
ycereal or heterocereal; scales cycloid or rhomboid, smooth or 
sculptured.” 
Of the above characters that which relates to the lobate fins is 
the essential one, and is the expression of the external appear- 
ance produced by the structure of the bones of the limbs already 
pointed out by Gegenbaur. The dorsal fins of some families, it is 
true, possess a remarkable structure, but in Phaneropleuron (Hux- 
ley) and some others they appear to be nearly like that of the 
Dipnoi. The absence of branchiostegal rays is important, but is 
shared by the sturgeons. The jugular plates appear to exist in 
Polypterus only among recent fishes, though several, as Amia, 
Elops, Osteoglossum, etc., possess a median one. Nevertheless, 
its nature would not lead one to anticipate its being a constant 
feature in any group of high rank; at least, such is our usual 
experience with dermal bones. The structures of the skin and 
scales given by Huxley are very subordinate. 
The remaining division answers then to the Teleostei and Gan- 
oidei of Miller, minus Polypterus. The name Teleostei cannot be 
preserved for this division, owing to its entire want of coincidence 
with that division of Miiller, as well as from the fact that the car- 
tilaginous sturgeons must be included in it. I propose, therefore, 
to call it the Actinopteri. The character of the five sub-classes 
will then be as follows: 
CLASS PISCES. 
The hyomandibular bone continuous with the cartilaginous cra- 
nium, with a rudimental opercular bone. Two distinct pelvic bones 
on each side. Derivative radii sessile on the sides of the basal 
bones of the limbs, separated from the articulation. Holocephali. 
Hyomandibular bone articulated with the cranium; no oper- 
cular or pelvic bones. Derivative radii sessile on the sides of the 
basal bones of the limbs, rarely entering articulation. Selachii. 
Hyomandibular bone articulated, with rudimental opercular 
bones; a median pelvic element. Limbs consisting of the axial 
line only, commencing with the metapterygium and with multi- 
plied segments. ipnoi. 
Hyomandibular articulated, opercular bones well developed; 4 
single ceratohyal; no pelvic elements. Limbs having the deriva- 
tive radii of the primary series on the extremity of the basal 
pieces, which are in the pectoral fin metapterygium, mesoptery- 
gium and propterygium. Crossopterygia. 
