LAliYNX OF MAMMALIA. 



587 



Balcenoptera is but little convex transversely ; the wings unite at 

 an open angle ; the breadth much exceeds the length, but the 

 lower angles are produced and continued down outside the cricoid : 

 this is a thick cartilage, broad and flat posteriorly, with a thick 

 upper margin and an irregular thinner lower one : it is incomplete 

 at the fore-part, from which the lining membrane of the larynx 

 protrudes and expands into a large sacculus. In Phoccena the 

 thyroid, from the great extension of the inferior cornua, seems to 

 consist of two semilunar car- 

 tilages united at their anterior 

 extremities. The cricoid is 

 incomplete at the fore part, 

 but does not give passage to 

 a laryngeal sac. The aryte- 

 noids, articulated to the cricoid 

 by a broad base, are of un- 

 usual size and length, rising, 

 in contact along their mesial 

 borders, and becoming in- 

 closed with the long epiglottis 

 by a sheath of the pharyngeal 

 mucous membrane, fig. 461, b, 

 so as to form therewith a long 

 pyramidal projection, with a 

 slightly expanded apex, which 

 is encircled, as it were 

 grasped, by a sphincteric dis- 

 position of the muscles of the 

 soft palate, ib. e. The open- 

 ing of the glottis (through 

 which passes the bristle, in 

 fig. 461) is transversely semi- 

 lunar in Delphinidce : it is 

 triradiate with the posterior cleft* extending backward between 

 the arytenoid apices in Balcenidce. The epiglottis seems almost 

 continuous, through its fibro-cartilaginous union, with the upper 

 margin of the thyroid: it is elongated, and curved toward the 

 arytenoids to which its lateral margins are attached, completing 

 the apical third of the laryngeal tube in Delphinidce : in Balcenidce 

 the epiglottis and arytenoids are relatively shorter, and are con- 

 nected together by the membrane at their base, the apices being 

 free and not expanded, as in Delphinidce. The bases of the 

 arytenoids extend from the cricoid forward to the thyroid, and 



Section of the Tongue, Pharynx and Larynx of the 

 Porpoise, cccxx. 



