LABYRINTH OF ORTHAGORISCUS MOLA L. 3 
The inner or median wall of the sacculus bears near its lower part a rather large 
roundish macula ; posterior to which is a smaller vertically elongated nerve-ending, 
corresponding to the papilla lagene. I could not find a trace of the ductus endo- 
lymphaticus. 
No otoliths of the kind usual in Teleosteans exist, but instead the macule are 
furnished with numerous small white rounded otoconia, aggregated together. Of 
these a very few have a cubical crystalloidal form, like those of Acanthias, but the 
majority are rounded or oval, rough on the surface, and concentrically striated 
within. 
The fish was unfortunately not fresh enough for histological study ; nor am I 
able to describe the course of the auditory nerve, which was cut short in removing 
the brain. 
The following are the dimensions of the parts :— 
Auditory cavity, ant. post. diam., - - - - 4.5 cm. 
- » vertical 5 - - = - 3.5 4; 
. 5, transverse ,, - - - - 3.0 ,, 
Utriculus, including recessus, length, - - - - 0.8 ,, 
Sinus superior, length vertically, - - - - WA op 
Canalis ant., length inc]. ampulla, - - - - BLO 5p 
2” post., ” ” ” i a z p 5.5 y) 
” ext., ” oy) » Z 2 A 6.7 ” 
Ampulla anterior, length, - - - - - - 0.4 ,, 
Tt is difficult to measure the semicircular canals accurately, and the anterior 
and posterior canals probably do not differ in length. Together with the sinus 
superior they practically equal the horizontal canal. 
The following features then are remarkable in the membranous labyrinth of 
this fish :-— 
I. In the complete conjunction of utriculus and sacculus, that is to say, in 
the absence of any distinction of pars superior and inferior, it differs 
from all other fishes (putting out of account the Cyclostomata) except 
the Lophobranchii. * 
II. But im the lack of separation between sacculus and lagena, it is of 
simpler construction even than the two Lophobranchiate genera whose 
auditory organ has been studied. In this respect it is approached, 
though not equalled, by its close allies Ostracion and Tetrodon, in 
both of which according to Rerzrus (though not in the Lopho- 
branch) the communication between sacculus and lagena is wide 
and open instead of being by a narrow foramen or duct. 
* See Rerzius on Stphonostema and Hippocampus, Gehérorg. d. Wirbeltiere, I., 1881, pp. 98-100. 
