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Show 1890.] HELODERMA SUSPECTUM. 203 serted into the posterior end of the corresponding arytenoid. The dilator muscle, upon either side, is superficial to the constrictor of the same side. The constrictors by their common contraction close the aperture of the glottis during the acts of respiration and deglutition. Dorso-laterally, the cartilaginous wall of the laryngeal box is ample and broad, while ventrally it is narrow; and its capacity is but slightly increased over that of the end of the trachea, which it surmounts. In m y female Heloderma the trachea, including the larynx, had a length of seven and a half centimetres, to the bifurcation of the bronchi, being composed of about 57 cartilaginous rings, each and every one of which are incomplete down the median dorsal line. Some few of these tracheal rings bifurcate, as we occasionally find them in Man. Either bronchus is unusually long, its rings being incomplete as they are in the trachea, which it lacks but little of having the same calibre. For instance, in this same specimen a bronchus measures three and a half centimetres in length, while its size changes but little from the bifurcation to its terminus, thus being nearly half as long as the trachea. According to Mivart, the bronchi in Lizards are usually "very short" (Encycl. Brit. vol. xx. p. 458), and to this rule Heloderma certainly forms an exception. A pulmonary vessel follows up either bronchus along its anterior aspect, as one does along the opposite side of the tube, each coming from the posterior portion of tbe lung. Either lung is larger anteriorly than it is posteriorly, ending behind in a rounded tip (see fig. 3, Plate XVI.), while it is in the fore part only that we find a pulmonic tissue of the finer more spongy sort, as these sacs behind are covered by a serous coat of a denser texture, and are filled in by air-cells of the larger more open kind, as is the case very generally in this class of Vertebrates. These lungs are of about the same shape, size, and length in our present subject, and their extremities within the abdominal cavity take up but little room. Now either bronchus curves slightly as it comes through the anterior moiety of the lung, and its rings are lost posteriorly in that part where the pulmonic tissue begins to become coarse. Bronchial branches are not definite, as communication is made with the lung-tissue by means of short-necked apertures found at a few points along their sides, principally anteriorly. VI. NOTES UPON THE ORAL CAVITY AND ASSOCIATED PARTS. At the roof of the mouth we have presented us for examination, posteriorly, the Eustachian pits. These are large and deep, especially behind; they shallow out as we proceed mesiad and towards the front. At the back part of either one of them there is situated the subelliptical aperture that leads into the organ of hearing, and these apertures, in a large specimen of Heloderma, are nearly 3 centimetres apart. Anterior to the point where the Eustachian pits cease, the lining membrane of the roof of the mouth is not so deeply |