204 DR. R. W. SHUFELDT ON [Apr. 1, 



pigmented ; while it fits very closely to the superimposed bones of 

 the skull, thus giving rise to several paired pits of greater or less 

 depth, and an azygos one that stands between the apertures of the 

 posterior nares. 



These latter are of fair size, somewhat rounded in outline, and 

 separated from each other by a transverse distance of nearly a centi- 

 metre in the adult. From either one there leads forwards a doubly 

 curved slit-like groove, the lips of which are flexible and in contact 

 by their edges for their anterior two-thirds. This groove terminates 

 in front in a small, rounded opening, which is the mouth-entrance 

 to the cavity containing the Organ of Jacobson. A line drawn per- 

 pendicular to the plane of one of the posterior narial openings would 

 be found to be considerably in front of the eve of the same side, and 

 still further in front of the brain. In the dried skull the direction 

 of the narial chamber lies longitudinally ; but in the living animal 

 the external nostril is laterally situated, so that an angle is formed in 

 the passage in front. 



The Tongue. — Boconrt and Boulenger have given a superior view 

 of the tongue in H. horridum, and it has been figured by other 

 anatomists. 



It is thick and broad at its base, rather thin and acutely but not 

 deeply bifid anteriorly. It is more than twice as wide behind than 

 it is in front, having rounded margins for its thicker parts. 

 Peculiar papilla forming epithelium is seen covering the hinder 

 two-thirds of its free surface, which is gradually developed from the 

 smoother coat of the fore part of the organ. A faint medio-longi- 

 tudinal groove marks its superior aspect, and it is bound down by a 

 thick median frsenum ventrally. Dissection shows it to be composed 

 of two symmetrical halves, which are separated from each other by 

 a thin fibrous septum, found in the medio-vertical plane. Posteriorly, 

 extending deep into its base, we find the rod-like body of the hyoid, 

 and about it considerable adipose tissue is deposited. 



Either lateral half of the tongue possesses two special muscles 

 that here require description : — 



120. The Lingualis. — This is purely an intrinsic muscle of the 

 tongue, which arises in the substance of its base, and, extending 

 longitudioally through the entire dorsum, its fibres are gradually 

 lost as it comes to the apex. It overlies the genioglossus and the 

 genio-hyoideus. 



121. The Genioglossus. — A muscle which must be considered 

 but partly intrinsic to the tongue I propose to describe under this 

 name. It is seen to arise, upon either side, from the inner aspect 

 of the mandible near the symphysis, and its fibres passing backwards 

 and upwards, spreading out as they do so, the muscle at once 

 becomes entirely incorporated in, and devoted to, the tongue. Its 

 insertion for the most part is limited to the hinder half of the organ, 

 extending from the frsenum to the base, and outwards as far as the 

 lateral margin. 



The broad, thick, fleshy, unensheathed and independent tongue 

 of Heloderma, then, is a very different affair as compared with the 

 [68] 



