120 CALIFORNIA ACADEMY OF SCIENCES. 



Family VI. HELODERMATID^. 



This family contains the only lizards which are known 

 to be poisonous. There is but a single genus, with two 

 species. The tongue is large, deeply divided at tip, 

 smooth anteriorly but villose posteriorly. The teeth 

 differ from those of other lizards in being grooved. 

 There are large poison-glands under the chin. The 

 limbs are well developed. The skin of all the upper 

 surfaces is covered with large tubercles which often 

 ossify. The belly is provided with squarish plates. 

 Usually there are no femoral or preanal pores, but one 

 specimen has a single preanal pore of great size. 



Genus i6. HELODERMA. 



Heloderma, Wiegm., Isis, 1829, p. 624 (type horridum). 



There are four pentadactyle limbs. The head is 

 covered with irregular, convex, bony plates, which often 

 coossify with the skull. The back and sides are pro- 

 vided with more or less regular rows of tubercles similar 

 to those on the head. The ventral plates are arranged 

 in transverse series. The eye has well developed lids 

 and a round pupil. The ear-openings are large. One 

 strong and usually one or more weaker gular folds are 

 present. 



34. — Heloderma suspectum Cope. Gila Monster. 



Heloderma /mspectutn, Cope, Proc. Ac. Nat. Sci. Phila., 1869, p. 5 

 (type locality Sonoran Region); Shufeldt, Proc. Zooi. Soc. 

 Lond., 1890, p. 148; Stejneger, N. A. Fauna, No. 7, 1893, 

 p. 194. 



Description. — Head and body depressed, large, heavily 

 built, with short limbs and tail. Upper surface of head 

 broad, flat, and covered with large, irregular, convex, 

 bony tubercles. Snout rounded. Temporal regions 

 swollen. Nostrils large, opening laterally between three 



