( 10 ) 



Pig. 2. The interior of the larynx of Orcella brevirostris, of natural dimensions. 

 By a yertical section the posterior wall of the chamber has been slit up 

 and the opposite moieties everted, the anterior, lateral walls and bottom 

 of the cavity, therefore, appear only to be those displayed : e., epiglottis ; 

 a., arytenoid cartilage ; c, cricoid in section ; ar., arytenoideus muscle in 

 cross section, on the right side, almost or as if continuous with (cap), 

 the crico-arytenoideus posticus ; ^., a vascular meshwork enclosed within 

 fibrous tissue and superficial to the preceding structures ; s, refers to 

 the multitudinous sacculations, both forming the floor and antero- 

 inferior laryngeal wall : a raised septal band occupies the median line 

 continuous with the main radial septse of the floor. 



„ 3. A view (natural size) taken as far as the middle line of the right side and 

 from behind of the lower part of the tubulif orm posterior nares of Flata- 

 nista. A segment of the protruding glottis is seen behind, to the right 

 and front of which the opened posterior nares show orifices of the eusta- 

 chian tube. This latter has a remarkable grooved and saccular character, 

 some of these representing communicating canals split up ; diverticula 

 being obvious : ph., cavity of pharynx ; e., epiglottis ; a,, arytenoid carti- 

 lage ;_p. n., posterior nares; eu^,, eu^., eustachian canal; cZ., diverticulum. 



„ 4. A sketch, also of natural size and from the same animal, of an eustachian 

 dilatation. As in fig. 3, it likewise is the right side, but from a different 

 point of view, viz., interiorly looking into the passage from the gular 

 sac prior to its opening into the posterior nares : t. indicates a tendinous 

 cord passing from wall to wall. 



„ 5. Another view of the eustachian sac of the P. gangetica, natural size. This 

 is on the left side, and also exhibits the characteristic septa sacculations, 

 ramifying channels, and chordae tendinese. 



„ 6. Anterior or under surface cartilages of the right moiety of the larynx of 

 Flatanista, E;educed to f th natural size. 



„ 7. Posterior or upper surface of same, fth natural size. 



8. Under surface of larynx of Orcella brevirostris, its right half reduced ^ 

 natural size. 



9. Posterior or upper surface of fig. 8, also ^ natural size. 

 „ 10. A ventral view of portion of the trachea of Flatanista gangetica, of natural 



dimensions. The peculiarities of the cartilaginous rings as described in 

 the text are here accurately displayed. 

 „ 11. A portion of the trachea of Orcella brevirostris, likewise natural size and 

 same aspect as preceding. 



3J 



3> 



PLATE XXIX. 



Fig. 1. Lungs, heart, and great vessels of Flatanista, ^rd natural size. 



2. The same parts in Orcella brevirostris, but somewhat more in natural posi- 



