240 VERTEBRATE ANIMALS. 
ORDER III. TELEOSTEI(Gr. ¢e/ezos, perfect ; and osteon, bone). 
—The fishes comprised in this order, as implied in their name, 
have a well-ossified or bony skeleton, and they are commonly 
known as the “bony” fishes. In all the Ze/eostez, the skeleton 
is bony, the skull is composed of distinct bones, and there is a 
lower jaw. The vertebral column always consists of more or 
less completely ossified vertebrae ; and the two pairs of limbs, 
when present, are in the form of fins, supported by rays. The 
gills are free, comb-like or tufted in shape, and always protected 
by a bony gill-cover. The dulbus arteriosus is not capable of 
regular contractions, and is separated from the ventricle by only 
a single valve. 
The order Zeleostec comprises almost all the most eonitae 
fishes, and it will be unnecessary to dilate here upon their struc- 
ture, as they were taken as the type of the class in describing 
the fishes generally. It may be as well, however, to recapitu- 
late some of the leading points in the anatomy of the bony 
fishes. 1. The skeleton is always more or less completely ossified, 
and does not remain cartilaginous throughout life. The noto- 
chord is not permanent, and the vertebral column consists of a 
number of distinct vertebre. The vertebrae, however, are “am- 
phiccelous,” or hollow at both ends, so that there is left between 
each pair a doubly-conical cavity, which is filled with the car- 
tilaginous or semi-gelatinous remains of the notochord, In this 
way an extraordinary amount of flexibility is given to the entire 
vertebral column. In no fish (except the Bony Pike, which 
belongs to another order) is the conversion of the bodies of the . 
vertebrze into bone carried further than this. 
2. The integument usually develops scales, and these in the 
great majority of cases are of the forms known as “ cycloid” and 
“‘ctenoid,” the former being circular or elliptical horny plates, 
with plain margins ; whilst the latter have their hinder margins 
cut into comb-like projections or fringed with spines (fig. 122, a, 0). 
3. The anterior and posterior limbs are usually, but not 
always, present, and when developed they are always in the 
form of fins. These fins may.be supported by “spinous rays” 
or “soft rays,” or by both. The spinous rays are simple undi- 
vided bony spines which taper to a point. The soft rays are 
doubly divided, splitting up towards their extremities into a 
number of secondary rays, and being also divided by transverse 
joints into numerous short pieces. 
