Mr. Bell on the Box Tortoises, 299 tteth of which have been figured in the above mentioned useful work. Plate X, Fig. 5. Profile view of the jaws magnified. •6. Lower jaw, natural size, left side, with the alveolar process removed, to exhibit the roots of the teeth. 7. Molarcs of the upper jaw, left side, magnified. 8. Molares of the lower jaw, left side, magnified. Art. XXXIV. A Monograph of the Tortoises having a moveable Sternum^ with Remarks on their Arrangement and Affinities, By Thomas Bell, Esq. F,L,S, When, amongst a group of animals agreeing in their general relatioDS, a number of species are found to differ from the rest in some important character, and that character connected with an essential difference in anatomical structure, we are justified in considering*those species as a distinct subordinate group, and, in a systematic arrangement, in applying to it a distinctive appellation. The subjects of the present memoir, were included amongst the Emi/des of Brongniart, and in their general appearance, as well as in the structure of the different parts, they certainly have con-siderable affinity with them. But the circumstance of their hav-ing the sternum separated, as it were, into two or three divisions, moveable upon each other, led Merrem to consider them as a distinct genus, to which he applied the term Terrapene, Since his work was published, Mr. Say, the excellent American Zoolo-gist, who appears not to have seen Merrem's book, has, in a paper on the freshwater and land Tortoises of the United States, also formed them into a distinct group, with the generic appellation Cistuda. As however the work of Merrem was published long before Mr. Say's paper made its appearance, I have retained the former name for one of the genera into which I have considered it necessary to subdivide them. M. Spix has also applied the
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