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anterior part has the same relation to the nasal capsule as the so-called posterior process 
from the maxillary in Amia, which has been dealt with above. Allis states further 
that this bone is pierced by n. olfactorius. I have observed myself that it extends ventrally 
so far downwards that it comes into contact with the vomer, and that the most anterior 
end of the palatoquadrate is attached to its ventral part. In these respects its ventral 
part thus shows conditions that make it probable that it is homologous with the 
preethmoid of Amia (Allis 1897 a, PI. XXI, figs. 8—10; 1898, pp. 446—450; 1909 a, 
pp. 17 — 22; Swinnerton 1902, pp. 580—533). The anterior dorsal part of the bone, which 
is covered by the nasals, seems at least to some extent to be homologous to the corres¬ 
pondingly situated part in Amia, i. e., according to what we can discover from the fossil 
forms, it should comprise at least the homologue of the anterior postrostral elements 
of the Rhipidistids. 
It is impossible at present to answer the questions as to whether the homologue 
of the posterior postrostral element of the Rhipidistids is also included in the part of 
the nasalo-ethmoid, which is covered by the nasals, or whether, together with the 
homologues of some posterior nasal elements, it formed the posterior part of the «nasalo- 
ethmoid», which is exposed behind the nasals, or finally, whether the posterior part of 
the «nasalo-ethmoid» is only to be taken as an anterior portion of the frontals, secondarily 
fused with the postrostrals. 
Finally, with regard to the nasals in Lepidosteus, it seems as if they were homologous 
with the corresponding ones in Amia, but, as will be clear from what has just been 
said, it is also possible that they correspond only to certain of the anterior nasal 
elements of the Rhipidistids. 
Palaeoniscids, Platysomids and Catopterids compared with Teleosts. 
With regard to the development of the neurocranium in Teleosts on the one hand and 
Palaeoniscids as represented by Birgeria on the other, I may refer to my account above 
(pp. 152—180). In addition, as in the case of Amia and Lepidosteus, I shall confine myself 
here as well to dealing with the homologues of the membrane bones on the dorsal side 
of the ethmoidal region. It may, however, be pointed out in this connection that our 
knowledge of the Teleosts is still very incomplete in this respect, and that there is still 
much to be learned before any far-reaching conclusions are possible. 
In Teleosts there is a paired, frequently rather narrow nasal bone, situated dorsally 
of the nasal capsule aud pierced longitudinally by the most anterior part of the supraorbi¬ 
tal canal. It may sometimes happen that the nasals ( Arapaima , Heterotis, Osteoglossum, 
Notopterus, Petrocdphalus; Ridewood 1904 a, pp. 69, 70) are developed in width in a medial 
direction so that they come more or less into contact with one another in the median 
line, as in Amia and Lepidosteus, covering, as Ridewood expressed it, the «mesethmoid.» 
In any case it will be clear that the nasals of the Teleosts are homologous with the 
similarly termed bones in the Rhipidistids, or more correctly speaking that they have 
been formed by fusion of the homologues of the nasal elements of these fishes. 
The so-called «mesethmoid» is developed rather differently in different Teleosts. 
It is generally unpaired and extends between the nasals of the two side backward to 
the anterior ends of the frontals. It may also, however, as in Esox (Huxley 1864, fig. 69; 
