After diligent work on chelonians by modern zoologists such as Dumeril, Bibron, Gray and Strauch, mentioning only the most important ones, we have discovered new forms of this small but interesting group of animals,and have enlarged science with knowledge about their habits. Much about their lives has still to be discovered and many facts have to be proved by further research. One of the most important questions is about the secondary sexual charateristics: These charateristics are the results of sexual selection, and in certain cases of the force of natural selection. Darwin gives little information [on chelonians] in his book The Decent of Man, where he gives much about secondary sexual differences in animals. There is also little [on chelonians] in Catestrini's recent work The Theory of Evolution, Torino 1877.

During recent years Gray did the most work about the external sex characteristics in chelonians, but we cannot be sure about his work, because we don't know the identity of the animals. I publish my research on a great number of living Testudo ibera Pallas from the Royal Museum of Turin. The external characteristics are controlled by research on the internal structure of the animals. Only the characteristic which are important for sexual differences are studied. Drawings were made of all these characteristics, for a drawing often tells more about natural history than many words.

1. Males are larger than the females, females are more convex and relatively more slender. The carapace at the back is larger in females.
2. Also the profile is different. Fig 5 gives the male and fig. 7 gives the female. The volume of the female carapace is larger for well known reasons.
3. The tail in the males is longer and wider at the base.
4. The cloacal opening is wider in males than in females.
5. The forelegs are a little longer in the males.
6. The areola is generally more clear in males than in females.
7. The nuchal scute is relativelly wider in males than in females.
8. In males the femoral scute is curved at the edges.
9. The costal scutes are smaller and longer in males than in females, fig. 7 and fig.5.
10. The last vertebral [central] scute in males is shown in fig.6 and in females in fig.8.
11. The fourth vertebral scute in males is shown in fig.9 and in females in fig.11.
12. The same difference is also found in the second vertebral scute.
13. The supracaudal scute in males is about as long as it is wide and the outside often has a spherical shape (fig. 1). In females the scute is wider than it is long, and the outside is often flat ⁽¹⁾.
14. There is a difference in the rear edge of the carapace between males and females (fig.3 and fig10).
15. The plastron is deeply hollow in males, especially in large individuals. In females the plastron is flat or a little convex.
16. The mobile part of the plastron is larger in females than in males and it is less wide (fig. 2). In males it is less mobile and relatively wider (fig.4).
17. The head is sharper in males than in females.
18. As a consequence of the shape of the supracaudal scute and the plastron, the distance between the supracaudal and the plastron is larger in males than in females.

These characteristics are clearer in adults than in juveniles. In some animals the characteristics are mixed, which can be explained by the theory of Darwin.

Figure legends

Males
Fig. 5 - Animal seen in profile, reduced in size.
Fig. 6 - Last vertebral scute.
Fig. 1 - Supracaudal scute with neighbouring scutes.
Fig. 9 - Fourth vertebral scute.
Fig. 4 - Hind part of the plastron.

Females
Fig. 7 - Animal seen in profile, reduced in size.
Fig. 8 - Last vertebral scute.
Fig.10 - Supracaudal scute with neighbouring scutes.
Fig. 3 - Supracaudal scute divided by a line into two parts.
Fig.11 - Fourth vertebral scute.
Fig. 2 - Hind part of the plastron.