CROCODILTANS. LIZARDS, AND SNAKES. 473 



tidte. It is characterized as follows: Teeth anchylosed by oblique 



bases. Premaxillary aud parietals sin<;le; frontal and nasals double. 



Interclrtvicle without transverse limbs. Hemii)euis flounced. Liver 



with hepatolateral mesenteries. Apical portion of tongue protractile, 



smooth. 



HELODERMATID.E. 



Tkeeoijloniv pleurodontes Waglkr, part, Syst. Amph., 1830, p. 163. 

 Trachydermis Wiecmanx, Herpt. Mex., 1835, p. 23. 

 Varaniens Dtr.MKRiL unci Bibkox, part, Erp. Geu., Ill, 1836, p. 437. 

 Helodermida; Gray, Proc. Zool. Soc, 1837, p. 132; Cat. Liz., 1845, pp. 3, 14. 

 Helodcrmidie Cope, Proc. Acad. Nat. Sci. Phila., 1864, p. 228; 1866, p. 322. 

 Trachydermi i/hjphodonta Bocoi'RT, Miss. Sc. Mex. Kept., 1878, p. 296. 

 Helodermatidai Boulenger, Ainer. Mag. Nat. Hist. (5), XIV, 18S4, p. 120; Cat. Liz. 

 Brit. Mas., 2d ed. ; II, 1885, p. 300. 



But one genus of this family is known, whicli is defined as follows: 



Ear expo.sed. A gular fold. Digits 5-5, witli a scries of transverse lamelLB infe- 

 riorly. Upper surfaces uniformly tubercular ; abdominal scales liat, juxtaposed. 

 Labial shields present Heloderma Wiegmaun. 



Heloderma is characteristic of the Sonorau region of the uearctic 

 fauna and adjacent parts of the neotropical. 



HELODERMA Wiegmann. 



Heloderma Wiegmanx, Isis, 1829, p. 624; Herp. Mex., 1834, p. 23. — Wagler Syst. 



Ampb., 1830, p. 164. — Dum^ril aud Bibrox, III, 1836, p. 499.— Gray, Cat. Liz. 



Brit. Mas., 1845, p. 14.— Eocourt, Miss. Sc. Mex., Kept., 1878, p. 296.— Bou- 



lenger. Cat. Liz. Brit. Mus., II, 1885, p. 301. 

 Trach yderma Wiegmaxx, Isis, 1829, p. 421 ; not of Latreille. 



Teeth fang-like, with slightly swollen base, rather loosel}^ attached to 

 the inner edge of the jaws, grooved in front and behind; teeth on the 

 pterygoid aud palatine bones. A strong postorbital arch ; pterygoids 

 and i)alatines widely separated; infraorbital fossa bounded by the 

 pterygoid, palatine, transverse bone, and maxillary. Head with bony 

 tubercles. Eyelids well developed. Limbs well developed; chivicle 

 slender; sternum divided longitudinally'. Skin of upper surfaces tuber- 

 cular, some of tbe»larger tubercles ossifying in the adtilt, of lower sur- 

 faces forming transverse series of squarish plates. No femoral or 

 preanal pores. Fore feet longer than hinder, with longer claws, the 

 digits nearly equal, the outer shorter. The roof of the mouth with two 

 separate fossa? for the posterior nares. and no median groove. Tongue 

 thick, fleshy, depressed, arrow-shaped, and a little bifid at tip, attached 

 along the median line, except for the terminal third. Tail not brittle. 



Several descriptions of the skull and parts of the skeleton of Helo- 

 derma have been i)ublished, but all of them are seriously defective in 

 not taking into account certain of the characters which are essential to 

 a true understanding of the taxonomic position of the genus. For the 

 following description I have before me two skeletons of the //. suspec- 

 trum belonging to the U. S. National Museum. 



Premaxillary with a large spine and a short alveolar portion; pos- 



