1891.] ON THE ANATOMY OF HELODERMA. 1 19 



6. On some Points in the Anatomy of Heloderma. 

 By Prof. C. Stewart. 



[Eeceived January 20, 1891.] 

 (Plate XI.) 



Having had an opportunity of examining the more or less entire 

 viscera of three specimens of Eeloderma, viz. a male and female of 

 H. suspectum, and one female of H. horridum, I have thought that 

 a comparison between them might be of interest, and also that it 

 was desirable to call attention to some features in which my specimens 

 appeared to differ from the recorded observations of others, and to 

 give a brief description of the male urogenital system of H. suspectum. 

 Dr. J. G. Fischer, in a paper published in 1878, has given figures 

 and a full account of the poison-apparatus, hyoideau muscles, &c. of 

 H. horridum. In the ' Proceedings ' of this Society for 1890 is a 

 very complete description of the anatomy of a female specimen of 

 H. suspectum by Dr. R. W. Shufeldt. 



Thyroid Gland. — The thyroid of H. suspectum is figured and de- 

 scribed by Dr. Shufeldt as a bilobed structure, the lobes united by a 

 transverse isthmus, and situated in front of the trachea at the base of 

 the heart, but in a footnote (op. cit. p. 206) he states that he may 

 have mistaken blood-stained tissue for the thyroid, but that he failed 

 to find anything else which resembled that organ. In all my speci- 

 mens it was readily found, as a paired organ, the lobes placed one 

 on each side of the trachea and totally unconnected by an isthmus. 

 They were surrounded by a well-defined capsule, to which they 

 were attached by trabeculse, the capsule apparently forming the 

 walls of a lymph-sinus. 



In H. Iwrridum the lower border of the thyroid is 47 mm. from 

 the base of the heart, and 73 mm. from the laryngeal opening. The 

 right lobe is 9 mm. long, 5 mm. broad, and 1| mm. thick. The 

 left lobe is 7 mm. long, with width and thickness the same as the 

 right. 



The lower border of the thyroid in the male H. suspectum is 46 

 mm. from the glottis, each lobe was 11 mm. long and Sg broad; 

 the extremity of the left lobe nearest the trachea was pointed, and 

 from the corresponding end of the right lobe there was a delicate 

 prolongation extending forwards, in length equal to that of the main 

 body of the lobe. In the female H. suspectum the thyroid was similar 

 in shape, but somewhat smaller than in H. horridum. 



Trachea, Larynx, and Lungs. — The length of trachea and larynx 

 from the glottis to bifurcation of bronchi was 1 10 mm. in H. horridum; 

 from bifurcation to point of entrance into lung 13 mm. There were 

 seven large openings from the continuation of the bronchus into the 

 lung-tissue, in front of its posterior termination. They are situated 

 on the ventral surface. Each of the posterior three shows more or 

 less a division into two, a condition more marked in other Lacertilia, 



