ORCELLA. 387 



The body of the arytenoid cartilage of Orcella is a laterally compressed oval, 

 with a sharp margin directed forwards and a rounded margin posteriorly, by the 

 upper two-thirds of which it is articulated to the cricoid by a synovial capsulated 

 joint. The inner surface is concave and the external flat. The anterior horn of the 

 cartilage is a long, laterally compressed and pointed structure in the upper half of 

 its extent, but in the lower half of its surface is thickened and convex from 

 side to side. It is connected to the arytenoid body by fibrous tissue, so that it is 

 freely moveable on it as is the case in Platanista. The posterior horn is a downward 

 prolongation of the anterior, and is a rounded bar of cartilage and terminates 

 abruptly in a flattened end at the lower portion of the penultimate sixth of the 

 arytenoid body, where it is capped by two small cartilages applied to each other 

 laterally, succeeded by another cartilage which is wedged in between them and the 

 last sixth of the arytenoids and curving forwards overlies them. A great part of 

 the attachment of the aryteno-epiglottidean ligament takes place from the outer 

 border of these cartilages. Lying between this apical cartilage of the joosterior horn 

 and its fellow of the opposite side occurs a small elongated nodulated cartilage 0"5 

 inch long and 0"12 inch broad, which assists in filling up the gap that exists between 

 the arytenoid and cricoid cartilages. It lies immediately below the mucous mem- 

 brane of the cavity, and is crossed by the longitudinal fold of the larynx. 



The cartilage of the epiglottis is shorter than the arytenoid horns, but of con- 

 siderable breadth, so as to embrace these structures by its lateral margins. It is 

 concave from side to side on its laryngeal face and strongly convex on its lingual 

 surface, expanding above the origin of the hyo-epiglottic muscle, from before 

 backwards, iato a thick club-shaped head with a rather pointed end. Its upper half 

 arches a little forwards, and its free end is rounded from side to side, and the margin, 

 scroU-like, curving forwards and backwards, terminates laterally in two thick 

 hom-like projections which turn backwards and support the anterior half of the free 

 border of the membrane of the arytenoid and of the cartUage of the epiglottis. 



When the mucous membrane is reflected from the side of the aryteno-epi- 

 glottidean membrane, it is seen to cover a complicated arrangement of valvular 

 passages separated from each other by piUar-like septa, and ramifying along 

 the sides of the base of the cartilage of the epiglottis. It is opposed to the honey- 

 combed mucous membrane of the inside of the larynx, and appears to be continuous 

 with channels which are displayed here and there surrounding the base of the larynx 

 above and below when it is cut longitudinally. This arrangement doubtless stands 

 in some relation to the glandular surface at the base of the larynx internally. 



Trachea (Plate XXVIII, fig. 11).— This is much more capacious than in Tlata- 

 nista, and its first portion is more imperfect and membranous. Two small flat carti- 

 lages depend from the cricoid, one being placed anterior to its posterior inferior angles 

 lying between it and the free end. These are succeeded by two imperfect rings, 

 each of which encircles about one-half of the tube, but they are separated anteriorly 

 by a membranous interval, whilst they largely overlap each other behind where the 

 lowermost one gives off a short offshoot to the right, from its upper border. The third 



