Dr. J. E. Gray on Chelontans. 289 



but with the aid of a more powerful microscope very fine and 

 numerous wavy strise are visible on the second volution only. 



The most nearly allied species appears to be V. Strangei, 

 Pfr., from which the present form is at once distinguished by 

 the different proportion of the last whorl to the others. In 

 Strangei the whorls increase more rapidly, and towards the 

 aperture the last one dilates very considerably ; this is not 

 the case in kermadeensis^ which is more transparent, more 

 glossy, and of a greener tint than the former. 



V. dimidlata^ Pfr., from New Zealand, the most nearly re- 

 lated species in a geographical point of view, is a very distinct 

 form. 



XXXIII. — Observations on ChelonianSj with Descriptions of 

 new Genera and Species. By Dr. J. E. Geay, F.R.S. &c. 



The shells of adult Land-Tortoises {Testudo) have the sternum 

 more or less deeply concave and the hinder marginal plate over 

 the tail (hence often called the caudal plate) very broad, thick, 

 and convex externally, and with the lower edge more or less 

 inflected. These I believe to be the shells of males ; and the 

 few specimens of the animals that I have been able to examine 

 confirm this idea. The other specimens have the sternum flat 

 and the caudal plate narrower, thinner, and flat, with the lower 

 edge more or less expanded. These have been concluded to 

 be the females. The shells of both the adult and younger 

 specimens have this form ; and as there must be young m.ales 

 as well as females, I conclude that some of the young shells 

 are those of males, and that the concavity of the sternum and 

 the width and convexity of the caudal plate are not attained 

 until the animal has arrived at the adult age. The concavity 

 of the sternum differs in the various species ; but in some 

 species, as Testudo fabulata, it becomes very deep in the older 

 specimens, and accompanied by a contraction of the sides of 

 the shell. Specimens in this state were regarded by Spix as 

 a distinct species, under the name of Testudo Hercules. 



The sternum of some of the more terrestrial Terrapins, as 

 Geoemyda^ have the stenium of the adult very deeply and 

 broadly concave ; and some of the large specimens of American 

 Box Tortoises {Cistudo Carolina) have the sternum concave in 

 the centre and convex behind. The rest of the specimens, 

 and the three of C. mexicana^ in the British Museum, which 

 are all full-grown, have the sternum flat. It may he, that 

 we have no adult males of the latter. There is in the Museum 

 a specimen of Swankn which has the sternum very flat in 



Ann. & Mag. N. Hist. Ser. 4. Vol.xi. 19 



