272 THE GALAPAGOS TORTOISES. 
young as compared with the old of this species, or with the Galapagos tortoises 
of whatever ages. For example, the majority of the young of 7’. tabulata have 
two axillary scales on each side. They are not as seen in 7’. argentina Sclater, 
T. chilensis Gray, shown by Siebenrock, 1912, fig. 1, where the lower is the 
larger. The lower is much the smaller; in cases it is absent, in others, it evi- 
dently has fused with the upper, thus bringing about the condition obtaining 
in the Porto Rican specimen, normal in the Galapagos. There is evidence 
that the single axillary is not excessively rare: it was figured by Schoepff, 1792, 
Pl. 13-14, as T. tabulata Walb., by Spix, 1824, under the synonym 7. sculpta, 
Pl. 15, and by Bell, 1835, Mon. Testud., Pl. —, Sowerby and Lear, 1872, Pl. 14, 
under 7’. carbonaria Spix, Pl. 16, another synonym. The young of 7. tabulata 
vary greatly in color, from yellow to black. On the back, whether light or 
dark the areolae are commonly yellow to orange, the color being more limited 
on the black individuals. On the majority the lower surfaces are yellowish, 
as to a considerable extent on the Galapagos. Specimens of less than six inches 
have marginal denticles on a thick swollen sternum, more or less produced, 
notched, and angled in front, etc., and they differ in some of the same features 
from the large or the aged of the species and from the Galapagos of whatever 
size, age, or species. The typical forms described as species of the latter have 
most often been chosen from the adult or the aged and these have provided the 
distinguishing characters from those induced by age. Among the old the greater 
difference exists and from them the more one approaches the newly hatched 
the more alike the specimens appear. This is what should be expected in 
cases of close genetic relationship. Comparing the tortoise of northern South 
America with those of the Galapagos it is found that the nearer approaches 
from the one to the others are the farther from the egg and mainly made by 
T. tabulata. Yet it is very doubtful if such close affinities would have obtained 
without the aid of a common ancestor. The results of all the comparisons 
made in this study tend to the conclusion that the origin of the Galapagos 
tortoises is directly connected with the species 7. tabulata of northern South 
America. 
