The osteology of Cromeria nilotica and Galaxias attenuatus. 63 
not extend anteriorly beyond the level of the eyeballs; but in this 
fish it extends to the level of the nares; and the cranial cavity itself — 
to that of the preethmoid cornua. That portion of the cavity which 
lies in front of the brain is filled with fatty tissue. Dorsally there 
are three fontanelles in the chondrocranial roof; a median one lying 
in front of the epiphysial bar (Fig. G as) and covered by the fron- 
tals; and two small lateral ones lying posterior to this bar and closed 
above by the parietals. The epiphysial bar is massive and is largely 
ossified by the extension of the alisphenoid along it. Posteriorly a 
similar bar of cartilage, separating the lateral fontanelles, unites it to 
the occipital region and enables the supraoccipital bone (Fig. E oc. s) 
to extend forwards between the hinder halves of the parietal bones. 
The roof of the chondrocranium thus conforms to the type shown 
elsewhere!) to be characteristic of non-ostariophysous fishes. 
Owing to the absence of orbitosphenoids, and to the suppression 
of the posterior portion of the trabecular region of the cranial 
floor, the cranial cavity opens into the orbit by a large fontanelle. 
As the cartilaginous lateral walls still remain in the anterior region 
(Fig. G) the olfactory nerves do not enter the orbit, but pass out by 
a separate foramen opposite the parethmoid bones. 
All the otic bones, except the opisthotic, are present and are separ- 
ated from one another externally by cartilage, which internally encloses 
the three auditory canals. 
The eyemuscle canal is closed ventrally by the parasphenoid and 
opens posteriorly in the region of the basioccipital. 
A small membrane bone (Fig. E e.p.b! and Fig. C) lying dorsal 
to but not fused with the parethmoid may perhaps be best spoken of 
as. a dermo-parethmoid ?). 
The vomer is edentulous, and free from the parasphenoid. 
In the hyosuspensorial apparatus of Cromeria the chief feature to 
be noticed is the absence of a symplectic (Fig. B). At first sight, 
owing to the position of an enormous anterior extension of the hyo- 
mandibular, one is liable to mistake the metapterygoid (pg.m) for this 
bone. That this cannot be, is proved by the fact that, unlike the 
true symplectic in other Teleosts, (cf. Fig. C sym) it has no carti- 
1) SWINNERTON, H. H., in: Quart. J. microsc. Se. V. 45, 1902, 
pp. 525, 526. 
2) CEE c. p. 531. Brinen, in: J. Anat. Physiol, V: 11, 1872, 
speaks of a dermo-prefrontal in Amia but SAGEMmEHL, in: Morph. Jahrb., 
1884, says it is fused with the underlying cartilage. 
