1890.] HKLODEKMA SUSl'ECTUM. 155 



state of things coiitiuues all the way to the root of the tail, with 

 scarcely any perceptible difference lu the size of the individual 

 tubercles, although perhaps the larger ones may range along the 

 middle of the back. They are so arranged that any single tubercle 

 in one row stands opposite the inlerspare between two other tu- 

 bercles either in the row in front of or behind it. When the 

 Heloderni is fat and in good condition, the individual tubercles 

 stand apart fiom each other, separated by a distance etjual in any 

 case to about the diameter of the base of the tubercle next to the 

 space. And when the reptile is laying out perfectly straight and at 

 rest, these several rows of tubercles seem to be separated from each 

 other by crease-like lines marking the intervening skin ; but the 

 moment the animal twists to one side or the other, these transverse 

 lines are immediately obliterated, while oblique ones, running straight 

 down the concaved side, take their place. As I have already 

 described above, these knob-like tubercles of the dorsal aspect of 

 the Heloderm's body m passing down the sides gradually assume the 

 flat scale-like type. From between the armpits and the groins 

 these are of an even oblong form, arranged in regular transverse 

 rows, being in contact with each other, while the individual scales 

 of one row break joints with the scales in front of and behind them, 

 much in the same manner as bricks in a building do. Between 

 the legs in front these oblong scales gradually assume a rounded 

 form, and in passing still more anteriorly they become still smaller, 

 to eventually merge into the minute tubercles, already described, that 

 cover the throat. These ventral scales also become more rounded 

 as they pass between the hinder pair of limbs, as well as slightly 

 smaller. The two middle preanal scales are markedly larger than 

 the few remaining ones that make up this row upon "either side of 

 them ; and, as 1 have already said, the tubercles on the posterior 

 margin of the vent are quite minute in comparison. The tubercles 

 covering the dorsal aspect of the great rounded tail of this reptile pass 

 regularly from those on its back, having the same arrangement and 

 character, only they are placed closer together, being nearly or quite 

 iu contact with each other. Further, as these caudal tubercles pass 

 round to the underside of this appendage, they, too, become gradually 

 flatter, but in their case only two middle rows running the leugth of 

 the underside of the tail may said to be flat. The rows of small 

 tubercles covering any one of the limbs are arranged much after the 

 same fashion as are those upon the back, while upon the soles of the 

 feet they are seen to be very much worn. Any single toe shows a 

 transverse arrangement of its single row of oblong scutes, both upon 

 its ventral and dorsal aspect, and between these, on either lateral 

 surface of the digit, is another longitudinal row of rounded scales, all 

 three being carried down so that the terminal ones surround the claw. 



As has already been hinted at in a foregoing paragraph, in 

 shedding but small patches of skin come away at a time, and these 

 show a perfect casting of the scales or tubercles they originally 

 covered. 



Of other Parts which may be examined externally. — By the aid 



