TRIASSIC FISHES FROM SPITZBERGEN 
155 
has also pierced the prootico-opisthotic and has been situated entirely in this bone. 
Both te saccplus and the utriculus seem to have been situated in the part of the 
labyrinth region occupied by the prootico-opisthotic, but it is difficult to say to which 
extent they were directly surrounded by this bone. 
We shall now briefly consider the ossifications of the capsula auditiva in a number 
of other Teleostomes for the sake of a comparison with the conditions in B. mougeoti. 
In the Teleostei the prootic, pterotic 1 ) («squamosal>>), epiotic, lateral occipital, basi- 
occipital, supraoccipital and, although rarely, the sphenotic 2 ) may help to surround the 
labyrinth (Vrolik 1873, pp. 278—290; Sagemehl 1884, pp. 81 — 85; 1891 pp. 573—574; 
Goodrich 1909, pp. 266; Allis 1899; 1909a, pp. 47, 56, 57, 59, 60; etc.). Among these bones 
the lateral occipital, epiotic and sometimes the supraoccipital are related to the posterior 
semicircular canal, the pterotic and the lateral occipital to the external one, and the 
prootic and sometimes the autosphenotic as well to the anterior one. The sacculus and 
utriculus are situated in a recess, formed anteriorly by the prootic, posteriorly by the 
lateral occipital and not infrequently by the Shmp.il k Ffr 
basioccipital as well. The so-called opisthotic 
has nothing to do with the labyrinth (Vrolik) 
and, apart from the Gadidae is weakly de¬ 
veloped. In the Gadidae, however, it forms 
part of the boundary of the foramen vagi, 
is pierced by n. glossopharyngeus and ex¬ 
tends considerably forwards in the lateral 
wall of the labyrinth region. Otherwise in 
the Teleostei it is generally a small bone, 
situated on the edge between the posterior 
and lateral surfaces of the neurocranium, 
without any great extension forwards on the 
latter surface. It is loosely attached to the 
adjacent bones and easily falls of during 
maceration. On it there is attached a ligament from the ventral process of the supra¬ 
scapular and in its reduced condition it is probably to be taken, as Allis (1899, 
pp. 49—60) and Sagemehl (1891, pp. 556—558) have emphasized, only as a fibrous 
ossification. 
In Amia, according to the view put forward by Allis (1897a, p. 688; 1897b; 
1899, pp. 60—62), only the prootic has been related to the labyrinth. Contrary to 
Sagemehl (1884, p. 188; 1885, p. 45) he considers the opisthotic in this fish to be an 
investigating bone. The opisthic there extends from the lateral occipital, together with 
which it sourounds the foramen vagi, forwards on the lateral wall of the neurocranium for 
a considerable distance and joins a backward pointing process from the prootic (Sagemehl 
1884, PI. X, figs. 2, 3 , 6; Allis 1897a, PI. XXI, fig. 10; Goodrich 1909, fig. 237). Ventrally 
of this process the cranial wall, which at this place is cartilaginous, is pierced by 
*) We only deal here with its primary component. 
2 ) We consider here only the autosphenotic or, where this is fused with the dermosphenotic («postfrontal»), 
the corresponding component of the compound bone. 
