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



These bands are unbroken in my smaller specimen, but in the larg;er 

 one a single imperfect row of orange tubercles passes round the middles 

 of the mid black bands, which are double on the black band next 

 the body, while two or three scattered black tubercles are seen upon 

 the intermediate orange bands. 



From rather above the knees and elbows down to the tips of the 

 several digits all four of the limbs in my smaller specimen are of a 

 uniform shiny jetty black, which is not the case in the larger indi- 

 vidual, where these parts are irregularly marked all over by both 

 black and orange. At present I am unable to state whether or 

 not these markings change at all with the growth of the animal, 

 but I am rather disposed to think that they do not. Moreover, I 

 have had Heloderms under my observation for two years at a time, 

 and during that period never knew the animal to shed its skin, as do 

 some other lizards and snakes. When I say this, I do not mean to 

 imply that a shedding never takes place, because that would not be 

 true, for at the present time (March 7th, 1888) the skin is shedding 

 from the toes and soles of the feet of my larger Heloderm, leaving the 

 scales bright and new as it comes away. What I do mean is that I 

 have never observed it peel off in great pieces, as it is known to do 

 in some of our Lacertilians, where I have frequently seen it slip off 

 nearly entire, forming a tissue paper-like cast of the entire form of 

 the lizard. 



Of the Form.— For the first few years of its life, the Heloderm 

 has a broad oval outline to its head, but as the animal matures this 

 !s superseded by the marked triangular form, where the angles at 

 the muzzle and opposite the mandibular articulations are rounded off, 

 and we may add that at all ages the head of this lizard is always 

 much depressed, being quite flat on top, while considerable fulness 

 pertains to the throat posterior to the mandibular symphysis. When 

 the animal is asleep we may by close observation see his sides swell 

 and collapse very slightly as he breathes, and at such times, too, the 

 most lax and posterior part of this throat-region perceptibly pulsates 

 in synchronism with the animal's respiration. Sometimes he has a 

 way of taking several quick breaths in rapid succession, when all these 

 movements become much more obvious. The body of this lizard is 

 of an elongated ellipsoidal form, being depressed, so that on section 

 at about its middle it would show an ellipse with its major axis 

 horizontally disposed. The tail is large and heavy, being subcorneal 

 in form, gradually tapering to a pointed tip ; the posterior hnibs 

 spring from points at its junction with the body, and as the latter is 

 considerably broader just beyond this point, it always gives the casual 

 observer the impression that these hind limbs arise from the sides of 

 the tail. No such deception ever strikes one upon viewing the 

 anterior pair of limbs, as in that region the neck is proportionally of 

 considerably larger calibre than is the root of the caudal appendage. 

 There is but very little difference either in the bigness or the length 

 of any of the limbs, though it may be slightly in favour of the 

 hinder pair, while for their entire lengths they are much of the same 

 calibre, showing only slight constrictions therein at the knees and 



