
Fune 22, 1871) 
NATURE 
147 

ear-shaped unossified pre-frontals, or lateral ethmoids. 
The median ethmoid is ossified entirely by the thick, 
bony bar, which commences as a knife-shaped vertical 
plate, or parostosis ; here in the eel as in the Amphibia, 
the distinction between parostosis and endostosis at 
times breaks down, 
the parasphenoid withits long style, as far back as the 
pituitary space ; it coalesces with the ethmoid when the 
eel is five or six inches in length. _ Where the bony 
ethmoid and vomer unite there is a groove; along this 
the olfactory crus runs, protected outside by the grooved, 
soft, lateral, ethmoidal wing, which arose as an outgrowth 
of the trabecular bar; the “cornua” of the trabeculze (Fig. 
C) persist as filiform prolongations, continuous with the 
lateral ethmoids behind, and end in blunt points near | 
the fore part of the ethmo-vomerine bony mass. In the 
conger, but not in the eel, the vomer sends out a wing on 
each side for the lateral ethmoids to rest upon, 
The long tooth-bearing vomer splits | 
| evidently the distinct foramen for the “portio dura.” 

| 
The | 
parasphenoid is very deeply split at both ends, both for 
the vomer and the basi-occipital; it has large wings 
in the basi-temporal region, which underlie, in a 
squamose manner, the‘ lower edge of the prootics. 
These latter bones divide the foramen ovale; behind 
and below the posterior opening there is a small passage 
The vomer and parasphenoid are azygous splints applied 
to the under surface of the coalesced and metamorphosed 
trabecular bars. 
When the membranous cranium dips downwards in 
front (mesocephalic flexure) then the trabeculz are not 
only parallel with the base of the first cerebral vesicle, but 
also nearly so with their immediate successors, the 
mandibular bars; whilst thus contiguous they form a 
secondary connection, which, of course, lengthens as the 
trabeculz ascend with the cranial sac, and thus enlarge 
the mouth cavity. This bar is well chondrified in fishes 

Fic, A.—InnerR View oF MANDIBULAR AND Hyorp ARCHES OF A YOUNG EEL, 23 inches long : 
g-quadratum; a articulare ; d@. dentary ; cr. coronoid ; mh. 
pterygoid ; #.Ag. pterygo-palatine ; 
sphenoidal region ; 
Fic. C.—SECTION THROUGH THE Nasat REGION OF THE SKULL OF A YounG EEL, 5 inches long: ef, 
tr. c. trabecular cornu. 
». pg. rudiment of cartilaginous 
g : Teckel’s cartilage ; 
fm. hyo mandibular ; sy, symplectic; s#./. stylo-hyal ; e.4. epi-hyal; ¢./. cerato-hyal ; 0/.f. opercular process ; 
mp p. metapterygoid process. 
Fic. B.—SEcTION oF ANTERIOR SPHENOIDAL REGION IN A YounG EEL, 
5 inches long: ef#. ethnoid; 7# frontal ; 0.5. orbito- 
tr. trabeculz : fa.s. parasphenoid ; 7. vomer ; c. ¢. cranial cavity. 
;, 
A. 
ethnoid ; 7. vomer ; 
All the figures are magnified about 25 diameters. 
generally, and in the tailless Amphibia. In the tailed 
Amphibia it is abortively developed, and no solid hyaline 
cartilage is found in this part in Sauropsida and 
Mammals. (See ‘‘ On Skull of ose Phil. Trans., 1869, 
1. 8c, figs. I, 3, 6, 10, and 11, p. 767. 
3 The a atee, has no solid cartilage in this bar, save a 
slight rudiment behind, as in the “ Urodela” (Fig. A), and 
the three ectostal plates that invest the large cartilaginous 
bar in most osseous fishes—the palatine, meso-pterygoid, 
and pterygoid—are represented by a needle-like, solid 
style of bone, pointed in front, and pedate behind where 
it attaches itself to the inside of the front edge of the 
quadrate. In old eels this style becomes a flattened bar, 
articulating by a squamose suture with the quadrate, and 
loosely attached to the lateral ethmoid and the maxillary 
in front. This bone is the counterpart of the single plate 
in the Lepidosiren’s mouth (see Huxley’s Elem., Figs. 
84 and 85, D, pp. 208, 209) ; but the pterygo-palatine of 
that fish is applied to a thick cartilaginous connective 
that fills in the whole sub-ocular region. As in the 

Lepidosiren and the Amphibia, tailed and tailless, the eel 
has only one ossification on the pier of the mandibular 
arch, and the generalised nature of the fish is shown in the 
partial coalescence which takes place between this and the 
succeeding (hyoid) pier. In the Lepidosiren, as in the 
Chimeera, the coalescence is entire between all but the 
free segmented rays of the first and second post-stomal 
arches ; in the Urodelz we have a similar state of things, 
but in the Anoura coalescence only takes place in the lower 
half of the pier. [In all these it is cartilaginous con- 
fluence, but in the eel it is merely the anchylosis of the 
bony symlectic (Fig. A, sy., g.) with the quadrate. 
Although there is no metapterygoid perched upon 
the quadrate, yet that element sends upwards a meta- 
pterygoid process which runs between and within 
two large denticulations of the hyo-mandibular. This 
latter bone (/m.) is very massive, and being most 
strongly united both by synchondrosis and deeply serrated 
suture to the quadrate, the suspensorium of the eel is ex- 
ceedingly strong, quite as strong as, and more elastic than, 
