DR. J. MTJEIE OjS THE ANATOMY OE THE SEA-LION. 547 



stylohyals are connected by fibro-cartilage to separate osseous elements, the epihyals ; 

 each of the latter bones is longer than the stylohyal, i.e. T4 inch, somewhat stouter, 

 dilated at both extremities and laterally compressed in the middle. Another fibro- 

 cartilaginous synovial hinge-joint passes between the epihyal and the much stouter, 

 equally lengthened adjoining bone. This, the ceratohyal, is subtriangular on transverse 

 section, a broad surface or border being ventrally situate, and the angular edge deeply 

 placed. The end of each bone which lies in apposition with the basihyal is enlarged 

 and slightly depressed or grooved internally. The single basihyal, 2T inch in length, is 

 developed as a stout bar of solid bone, with wide flattened extremities, possessing a 

 superior and inferior or anterior and posterior broad facets ; with these the ceratohyals 

 articulate above, and the thyrohyals below. The middle or body of the basihyal is 

 somewhat narrower than the extremities, and is compressed in an opposite direction to 

 the ends. Each thyrohyal is knobbed at its basihyal end, and tapers to a narrow car- 

 tilaginous point at the thyroid extremity. It is subcompressed laterally, slightly bent 

 or arched forwards, roughened or with a median prominence in front, and rather 

 sharper-edged behind. Length 2-2 inches. At their narrowed cartilaginous tip is a 

 free triangular nodule of cartilage - 4 inch long, the so-called cart it ago triticea. This 

 is connected by strong fibrous tissue to the thyrohyal and is also attached by the lateral 

 thyrohyoid ligament to the superior or anterior cornua of the thyroid cartilage. 



b. Cartilages of the Larynx. — Thyroid Cartilage. The two alae as they approach 

 together in front are deeply incised anteriorly and posteriorly (or above and below), 

 leaving only a narrow but nevertheless thick and strong septum of communication 

 (pomum Adami). The anterior notch is an inch deep, the posterior no more than half 

 that. Each lamella is somewhat rhomboid in form, the superficial and deep borders 

 (anterior and posterior in Man) being convex, the anterior somewhat and posterior 

 (upper and lower) decidedly concave. There is no prominent oblique line or ridge ; 

 but on the lateral surface and near the middle of the posterior (inferior) concavity is 

 a large-sized roughened tuberosity to which the arytenoid and thyro-arytenoid muscles 

 are attached. The posterior (inferior) cornu is half an inch long, ending in a rigid 

 thickened pointed extremity ; the posterior crico-arytenoid muscle being fixed thereon. 

 The anterior (superior) cornu is much smaller, thinner, and elastic. Internally, the 

 surface of the thyroid lamella is perfectly smooth. The connecting bridge between the 

 ala?, much stouter than they, is smooth externally, but has an elevated cartilaginous 

 median papilla within, from which the vocal cords arise. Measured from the septal 

 junction to the deep free margin, each thyroid lamella is 1\ inches ; from the summit 

 to the cricoid end 2 inches, the distance between the extremities of the cornua being 

 nearly the same. At the narrowest part, between the anterior and posterior convexity, 

 it is 1 j inch in diameter. 



The cricoid cartilage forms a solid ring some 6 inches in external circumference. 



