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Show 556 MR. G. A. BOULENGER ON EMYS BLANDINGII. [June 23, its length (from the extremity of the plastron) being contained twice and two thirds in the length of the shell in the adult male, and four times in the adult female ; in the quite young, figured by Agassiz, about once and a half. In the adult male of E. orbicularis the length of the tail is contained about once and a half in the length of the shell, in the female twice to twice and one fourth ; in the quite young, tail aiid shell are of equal length. I count 27 caudal vertebrae in the skeleton of E. blandinyii (adult female) in the Museum, and 31 in a skeleton of a female E. orbicularis. Other differences are to be found in the coloration of the head, the lower jaw and throat being of a uniform yellow colour, contrasting with the dark brown of the upper jaw ; and in the colour of the iris. This is of a bronzy brown in the female and reddish brown in the male. Similar sexual variations in the colour of the iris are known to occur in Cistudo Carolina. In the newly-born Emys orbicularis the iris is of a uniform dark brown ; as the animal advances in age small round yellow spots, similar to those on the sides of the head, appear on the iris, and gradually increase in size until, in the adult, the iris is principally, or even entirely, yellow. A few words as to the habits, so far as I have been ahle to observe from the two specimens lent m e by the Society, and which I kept for a couple of weeks in company with specimens of the European species. Holbrook says, " It is known to be a land animal, and found about the meadows and prairies of the West." I am not able to confirm the statement that it is terrestrial. The Society's specimens go to the water, though less readily than their European congeners; they dive and feed in the water. When disturbed on land they usually seek shelter by withdrawing into the shell, as do Land- Tortoises ; whilst E. orbicularis, under similar circumstances, makes for the water. When handled, the timid E. blandingii nearly always retires into the shell, whilst even fresh-caught specimens of E. orbicularis seldom do so. To conclude, it may be observed that, though belonging unquestionably to the same group as E. orbicularis, E. blandingii shows in some of its characters, shorter tail and coloration of the iris, as well as in its less aquatic habits, a certain approach to its American allies of the terrestrial genus Cistudo. EXPLANATION OF PLATE L. Fig. 1, Emys blandingii, Holbr. 1 a. Head of male, side view. 1 b. Ditto, upper view. 1 c. Ditto, lower view. 1 d. Head of female, side view. 1 c. Skull of female, upper view. 1 /. Ditto, side view. 1 g. Mandible, lower view. Fig. 2. Emys orbicularis. 2 a. Head of male, side view. 2 b. Ditto, upper view. [. 2 c. Ditto, lower view. 2e. Skull of female, upper view. 2 / Ditto, side view. 2g. Mandible, lower view. |