EEL-FISHES. 
1015 
of the first (posterior) hypural bone. A continued re- 
duction would thus seem to obtain here; and the di- 
phycercal caudal fin of the Eel, a character which would 
else be the token of a low degree of evolution, rather 
suggests a far advanced, retrogressive metamorphosis. 
Among the peculiarities that characterize the skull 
of the Eel, the first to attract attention are the com- 
paratively great expansion of the parietal bones (fig. 
268, par), which form almost half the roof of the cra- 
nial cavity, and the excessively elongated squamosal 
bones ( squ ), which by means of a long process on the 
upper side of the skull extend forward to a line with 
the hind extremities of the upper ethmoids ( et and etv ), 
and at about the middle of their length support the 
postfrontals (spho). The last- mentioned bones rest below 
on the petrosals ( ptr ), and have lost their importance 
as a point of suspension for the hind extremity of 
the suborbital ring. This (sob — pob), which in our 
common Eel — as well as the prefrontals (its anterior 
suspensories) and turbinals (spet) — is cartilaginous, is 
attached behind on each side of the skull to a process 
(fr in D), broken up into spines and originating from 
the side of each frontal bone just before the anterior 
extremity of the squamosal bone. The breaking-up of 
this process into spines, whereby firmer muscular at- 
tachments are secured, and which we have previously 
seen in the upper spinous processes of the anterior 
abdominal vertebrae, extends to the lateral occipitals 
(lo) and the squamosals, that expand backwards like 
wings, and, as well as the other bones in the lateral 
walls of the skull, are characterized by a spongy tex- 
ture. There is no orbito-muscular canal; and the true 
sphenoid (basisphenoideum, bsp in fig. 282) is closely 
superposed on the parasphenoid, with upward processes 
towards the descending processes (fr below in fig. 268, 
C) of the frontal bones and towards the alisphenoids 
(alsp) behind them. There are no orbitosphenoid bones. 
Great diversity of opinion still prevails as to the 
composition of the palatine and maxillary arches — as- 
suming that both these arches should really be re- 
garded as distinct in the present series. In that case 
each of them consists on each side of only a single 
bone. The inner bone (fig. 269, pt), in the common 
Eel of a thin and oblong, lanceolate form, often im- 
perfectly ossified in front, joins the oblique hyoman- 
dibular (Jim) and the quadrate (qu) to the anterior 
“ Zeitschr. Gres.' Naturw. 1867, p. 270, taf. I, fig. 1 («). 
part of the parasphenoid (fig. 268, psp). In the Con- 
ger it is expanded and bifid behind, one branch meeting 
the hyomandibular, and the other forming the con- 
nexion with the quadrate. The outer bone (fig. 269, 
mp) lies anteriorly and throughout the greater part of 
its length in the same plane a"s the inner, and is there 
united by ligaments with the latter, the two bones thus 
forming on each side a palatine roof continuous with 
the parasphenoid bone. But the hind extremity of the 
outer bone is twisted and bent downwards, and is folded 
outside the mandible, being united by strong, but loose 
bands of sinew to the outside of the coronoid process 
of the latter. In the common Eel this end is pointed, 
in the Conger flattened, somewhat expanded, and in- 
serted between the outer and inner bands of sinew by 
which the great cheek-muscles are attached to the man- 
dible. In the latter species the hind extremity of the 
outer bone also glides on the outside of the coronoid 
process of the lower jaw, by means of a flat and car- 
tilaginous, articulary surface on each bone. In the Mu- 
rama, according to Jacoby", it is joined by a special 
band of sinew to the outside of the quadrate. The an- 
terior extremity of the outer bone is tightly articulated 
with the compound bone formed by the coalescence of 
the vomer and the ethmoid (fig. 268, et, etv , and v ), 
a striking resemblance to the corresponding connexion 
between the intermaxillaries in the Pike, where we 
found the said bones (fig. 253, pmx) similarly furnished 
with a flat, ascending process. But here these processes 
(fig. 268, A) are so closely applied to the constricted 
and carinated anterior extremity of the ethmoid that 
they almost meet above, behind the expanded head of 
the vomer (etv, to the right in B). This connexion 
reminds us most of the ordinary position in the Teleosts 
of the palatine bones. The analogy between the outer 
bone and a palatine is further strengthened by the 
disposition of the teeth. In most of the fishes we have 
hitherto seen furnished with teeth both on the vomer 
and the palatines, the transverse row of teeth on the 
anterior extremity of the first-mentioned bone (the 
head of the vomer) forms an arch together with the 
palatine teeth, and here too the teeth are so arranged. 
The long and narrow vomer ( v ), the posterior end of 
which extends on the under side of the parasphenoid 
bone a little beyond the orbits in the common Eel, is 
armed underneath and in front, for rather more than 
Scandinavian Fishes. 
128 
