CAUDAL ABNORMALITY IN LIZARDS. 681 



In both cases the transverse section of the undivided proxima 

 region is slightly flattened laterally, as are those of both branches of 

 B. In A the left branch is much flattened laterally, while the right 

 branch is flattened dorso-ventrally. The branches of both tails taper 

 regularly to their extremities, except the ventral tail of B, which at 

 3*4 cm. from the forking is suddenly constricted, while the scales from 

 this point to the tip are much smaller than those of the rest of the 

 branch. These features suggest that injury and a second regrowth 

 have occurred in this branch. 



Scaling. — The scaling of the reproduced tail in lizards has 

 acquired much interest from the observations by Boulenger,* that in 

 certain genera the new scaling differs from that of the congenital 

 stump of the tail, and at the same time resembles closely that of some 

 other and possibly more primitive form. Reference should also be 

 made to the work of Werner § on this subject. In many genera, on 

 the other hand, the normal scaling is developed on the reproduced tail. 

 Mabuia carinata approximates to the latter condition. The normal tail 

 is covered on the dorsal and lateral surfaces by scales of nearly equal 

 size, while the median ventral surface possesses a series of larger 

 shield-like scales (fig. 1). When the tail is reproduced the scaling 

 resembles the normal, except that there is in this case a dorsal as well 

 as a ventral series of shield-like scales (fig. 2). I am indebted to 

 Mr. G-. A. Boulenger, F.R.S., of the British Museum, for information 

 on this point. 



In the present examples the scaling of the whole of the reproduced 

 portions agrees with what has been described above for the reproduced 

 tail. Moreover, compared with the normal scaling, the scales are 

 softer, lighter in colour, and those of the dorsal and dorso-lateral surfaces 

 exhibit only slightly or not at all the tri- or quinque-carination 

 characteristic of the scales of the normal tail. These features, how- 

 ever, are such as might be expected in a new structure. 



Branches of Specimen A.- — The dorsal and ventral series of large scales 

 of the undivided proximal portion appear to divide at the forking, and 



* " On the Scaling of the Eeproduced Tail in Lizards." — Proc. Zool. Soc. (1888), p. 351. 

 " On an Iguana with a Reproduced Tail."— Pro". Zool. Soc. (1891), p. 466. 

 Also in Mivart, " On the possible Dual Origin of Mammalia." — Proc. Roy. Soc, (1888), 

 XLIII, p. 378. 

 § " Ueber die Schuppenbe Kleidung des regenerirten Schwanzes bei Eidechsen."— Sitz, 

 Akad. Wien., 1896, CV. p. 123. 



