loO DR. R. W. SHUFELDT ON [-^pr- 1> 



da}' suns, and I have satisfied myself that upon these and other 

 occasions, when I have closely watched them, they possess to a 

 certain extent chameleonic powers, for I have observed the orange 

 part of their scaly armour pass from that colour to a decided salmon 

 tint and vice versa, remaining normally, however, at some shade of 

 orange or yellow. When thus sunning themselves they have a habit of 

 stretching their limbs backwards, even to the extent of having the feet 

 with their dorsal aspects in contact with the ground, the palms and 

 soles being directed upwards. They will then close their eyes and lay 

 in this position for hours at a time. So far as their pliysical strength 

 is concerned, it seems to be about equal to that of young Alligators 

 of a corresponding size ; they do not, however, possess the power of 

 striking a blow with the tail, enjoyed by the latter reptile. And in 

 getting over rough ground, where branches, large stones, or other 

 obstacles stand in the way, Heloderms evince no little patience, 

 ingenuity, and downriglit obstinacy in overcoming such barriers to 

 their progress. By a series of simple experiments 1 have been en- 

 abled to satisfy myself that the senses of sight, smell, and hearing 

 are all quite acute in these reptiles, and they are also sensitive to the 

 sense of touch. As to tiieir general intelligence, however, or such 

 mental attributes as they may be possessed of, I have made tio special 

 investigations, but from my casual observations I am inclined to 

 believe that they stand rather above the average reptile in both of 

 these respects. 



II. On the Form and External Characters of 



HELODEItMA SUSFECTUM. 



One of these reptiles in my possession is considerably larger than 

 the other, and by an approximate estimate only of their respective 

 lengths, for I intend to present exact measurements further on, I 

 would say that the smaller of the two was, from tip to tip, about 

 28 centimetres long, while the other has a total length of about 41 

 centimetres. The smaller one is by far, both in its markings and 

 general coloration, the handsomer of the two. 



My large Heloderma has a total length of 41 "3 centimetres and a 

 mid-girth of 18 centimetres, but this latter, of course, is very variable, 

 as the animal may alter it considerably by inspiration and expiration 

 at its will. 



Other measurements, which I have carefully taken, are presented 

 in the accompanying table, and they will give a fair idea of the pro- 

 portions of one of tiiese reptiles. It will be seen also that the relative 

 proportions vary with a^e. Moreover, as with all Vertebrates, these 

 profiorfions may actually vary for each individual, just as we find 

 robust and stout men to compare with slender and tall men. 



Table of Measurements. 

 (Measurements in centimetres and fractions.) 



Larger one. Smaller one. 



Total length 41-3 29-2 



Mid-girth (variable) 18-0 12-1 



