548 DE. J. MUKLE ON THE ANATOMY OF THE SEA-LION. 



Behind it is 2 inches in extreme (anteroposterior) depth ; in front, or superficially, 

 which is the narrowest part, it is 09 inch ; the diameter from the ventral to the vertebral 

 superficies is 2 inches. The elevated smooth ventral aspect is, as noted, moderately deep 

 and with biconcave margins. The oesophageal surface has a raised mesial line, with 

 lateral, wide, shallow excavations between it and the thyroid cartilages, the posterior 

 crico-arytenoid muscles completely filling these depressions. Where the arytenoid 

 cartilages are attached the cricoid on each side is very much thickened and projects in 

 a rounded manner, leaving a median deep cleft or notch, which is filled with fibro-fatty 

 tissue. The tracheal end of this same oesophageal surface has a thin spatulate cartila- 

 ginous plate - 3 inch long, and fully as much broad at its widest part. On each side of 

 this the borders are incised semilunarly, and form a slight angle posterior to (or beneath) 

 the thyro-cricoid articulation. 



Each pyramidal or trihedral, but round-margined arytenoid cartilage is of the fol- 

 lowing dimensions — 07 inch in extreme height, an inch in basal width, and - 6 inch 

 in thickness, or from the internal to the external surface. Its crico-articulating facet 

 is large, shallow, and with a synovial membrane. The inner mesially connecting spur 

 is the thinnest and most elastic portion, and possesses a rounded recurved point to which 

 the interarytenoid ligament is fixed. The true and false vocal cords have a firm and 

 strong bond of union. The posterior crico-arytenoid ligament loosely but powerfully 

 connects the cartilages in the interval. 



Fixed to the summit of the arytenoid cartilage by a close, movable, but not synovial 

 joint, is a smaller and softer V-shaped cartilaginous body, which, as a whole, includes 

 the cartilages of Santorini and Wrisberg. 



c. Laryngeal Membranes and Ligaments. — The thyro-hyoid membrane, or middle 

 thyro-hyoid ligament, forms a strong, wide, and very clastic connecting bridge between 

 the basihyal, thyrohyals, and thyroid cartilage. It contains in its centre, or midway 

 between the basihyal and the fore part of the thyroid shield, a firm, well-developed, 

 cartilaginous nodule. This nodule of cartilage has a short figure-of-8 shape, smooth 

 on the ventral surface, and rougher or somewhat carinate anteriorly on its deep aspect. 

 It is 08 inch long, and OS broad at its anterior segment. It is deeply imbedded in the 

 fat and fibrous tissue at the root of the epiglottis ; and between the latter and its internal 

 projecting anterior point there passes a strong fibro-elastic band — the hyo-epiglottic 

 ligament. 



The lateral thyro-hyoid ligaments are two narrow bands of fibro- and yellow elastic 

 tissue, which pass between the tip of the thyrohyals and each cartilago triticea to the 

 short anterior cornua of the thyroid cartilage. 



The crico-thyroid membrane, divisible by human anatomists into a mesial and two 

 lateral crico-thyroid ligaments, is, in Ofaria, a well-developed strong fibro-elastic struc- 

 ture, the median portion containing abundance of yellow elastic tissue, which is thick- 

 ened and forms a projecting ridge. The lateral portions of the crico-thyroid membrane, 



