290 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
by ligament. It is also firmly united by ligament to the upper por-— 
tion of the emhyal. 
8. THE SuUBOPERCULUM, 
As above indicated, is seen in the uppermost branchiostegal ray, 
which occupies exactly the position of the suboperculum in other 
Teleosts. 
The large anterior extension of the hyomandibular, whereby the 
metapterygoid is thrust forwards, is a characteristic feature. On 
examining a young stage it is seen that this extension is not an 
ossification originally represented by cartilage, but is a growth for- 
wards of the perichondral bone of the hyomandibular cartilage into 
the membrane lying in front. This appears to have been originally 
due to the relations of the R. hyotdeo-mandibularis N. facialis, the 
growth being later on carried still more forwards for the attachment 
of muscles. This has resulted in the hyomandibular usurping the 
position of the metapterygoid, and its functions as regards the origin 
of the musc. adductor mandibule, the longitudinal ridge usually 
being in the metapterygoid. 
The relations and origin of the opercular bones at one time aroused 
much discussion ; some light is apparently thrown upon these points 
by Amiwrus, but, before enunciating any theory, it may be well to 
state briefly the ideas of earlier authors. 
The earlier writers, such as Geoffroy Saint-Hilaire and Spix, were 
inclined to consider the opercular bones as comparable to the auditory 
ossicles of the mammalia. Thus the former terms the preoperculum, 
the ‘tympanal,’ the operculum, the ‘stapéal,’ the subopereulum, 
the ‘ malléal,’ and the interoperculum, the ‘ inceal ;’ while, accord- 
ing to Spix, the same bones are respectively, leaving out the subo- 
perculum, the ‘marteau,’ the ‘enclume,’ and the ‘ étrier.’ Cuvier" 
denies these relationships, saying ‘ 
plus on examinera les piéces 
operculaires, plus on se convaincra que ni leurs connexions entre 
elles et avec les autres os, ni les muscles qui les mettent en mouve- 
ment, ne présentent le moindre rapport avec les osselets dont il 
s’agit.” Neither deBlainville or Agassiz believed in the auditory 
theory, the former believing the opercular bones to belong to the 
1 Cuvier et Valenciennes.—Hist. nat, des Poissons. Paris, 1828. 
