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in connection with, the musculus levator arcus palatini. In Ceratodus 
and Chimaera this process is apparently wholly wanting, as is also 
a M. levator arcus palatini; in Chlamydoselachus it is but slightly 
developed; in Heptanchus it is largely developed and articulates with 
the dorso-lateral portion of the postorbital process of the chondrocranium, 
lying external to the trigeminus and facialis nerves, and to the external 
carotid artery and the jugular vein; in Amia it has a position similar 
to that in Heptanchus, but instead of articulating with the dorso-lateral 
portion of the postorbital process it is there connected with that process 
by a ligamentous band; in Lepidosteus it is found as the processus 
oticus of ParKer’s (1882) descriptions; while in teleosts it becomes 
attached to the hyomandibular either by contact or by ligament, and 
its relations to the trigeminus and facialis nerves, the external carotid 
artery and the jugular vein are obscured. It always lies, in all these 
fishes, dorso-external to the efferent pseudobranchial artery, and, in 
Amia and teleosts, dorso-external also to the secondary afferent pseudo- 
branchial artery when that artery is developed (Atuis, 1912). It would 
seem to be the homologue of the muscular process of Gaupp’s (1893) 
descriptions of Rana, but further investigation is certainly needed to 
properly determine its homologies. It might possibly be related to the 
rudimentary processus pterygoideus of Greiw’s descriptions of Ceratodus. 
The hyomandibular of Krawerz’s descriptions of Ceratodus, it may 
here be stated, is evidently nothing but a part of the lateral wall of 
the trigemino-facialis chamber, and the fact that this part of the walk 
chondrifies independently of the pars ascendens palatoquadrati seems 
further proof of the homology of the latter part of the palatoquadrate 
of Ceratodus with the lateral wall of the trigemino-facialis chamber of 
other fishes. The assumption that the lateral wall of this chamber of 
Ceratodus is of double origin, one component belonging to the neuro- 
cranium und corresponding to the wall of the chamber in Amia and 
teleosts, and the other component belonging to the palatoquadrate and 
corresponding to the processus metapterygoideus (then oticus) of the 
latter fishes, seems unwarranted. 
In the Holocephali, Huprecut’s (1877) descriptions of the adult 
Chimaera and Callorhynchus, and ScHavissLand’s (1903) descriptions 
of embryos of Callorhynchus, are both lacking in the details needed 
to definitely identify the trigemino-facialis chamber. But that chamber 
would seem to be represented in these fishes in the canal traversed 
by the nervus facialis as it perforates the so-called palatoquadrate 
