290 PROF. W. B, BEKHAM ON THE [Apr. 2, 



one side of the laryux, meeting its fellow at a distinct angle, 

 and so forming a ridge. 



The body is irregularly rectangular (PI. XXVI. fig. 6), with a 

 nearly straight but slightly curved ventral border having a thin 

 edge, a curved aaterior border presenting a recurved and thickened 

 edge, which passes dorsally with the posterior cornu : the posterior 

 border of each ala is oblique but straight, while the dorsal border 

 is curved, and passes forwai-ds to join the root of the posterior 

 cornu. 



These various " borders " pass into one another at rounded 

 angles, but the angle formed by the ventral and posterior borders 

 is better marked than the rest, and it is at this angle that the two 

 al^ — the right and left — approximate most closely ; nevertheless 

 they only just meet, and this when the apparatus is at rest. It 

 is here that the lower end of the epiglottis rests, as will be seen 

 later. 



The posterior cornu of the thyroid is a short, flat, narrow plate, 

 whose base passes quite imperceptibly into the dorso-anterior 

 region of the body, but between the cornu and the dorsal border 

 of the plate there is a well-marked " bay." 



Each thyroid plate is nearly flat ; it is only feebly convex in a 

 dorso-ventral direction (a convexity which is slightly exaggerated 

 in the figure of the ventral view); the edge is thin, except along 

 the anterior border, which is thick and everted, and probably 

 represents the " anterior cornu." 



The measurements of this plate are as follows : — 



The ventral border is 3 inches, measured along the curve. 



The posterior border is 2^ inches. 



The anterior border is Ij inches. 



The dorsal (behind the cornu) is 2 inches. 



The outer curve of the posterior cornu is 4J inches, 



while its inner (i. e. ventral) margin is about 1| inches, 



and its breadth | inch. 



In the Pilot Whale the figures and account given by Murie 

 show a very different thyroid ; the body, which is single, being 

 transversely extended across the ventral surface of the larynx, 

 while the posterior cornua are much longer, leaving a deep wide 

 bay on each side between themselves and the body. 



The cricoid cartilage (PI. XXVI. figs. 8, 9, 10) is a complete 

 ring, and, as usual, is of greater height (i. e. antero-posterior 

 length) on its dorsal half than on its ventral. 



The dorsal half of the ring is a broad thick band, deeply 

 excavated on its binder margin, while its anterior margin is 

 irregularly convex ; when viewed from this aspect, then, it has the 

 appearance of an inverted V with a very open angle (about 90°) 

 and thick limbs. 



The median line of this dorsal face projects as a slight 

 convex ridge, separating the right and left muscular fossa? from 

 one another. The sloping sides bear on the upper margin the 



