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Show 296 DR. J. E. GRAY ON RHINOCLEMMYS MEXICANA. [Apr. 4, Bradycinetus brenda. Fig. 6. Mandibular foot of male: a, mandibular process. PLATE XXVII. Philomedes folinii. Fig. 1. Carapace of male, outline, seen from left side. X 20. 2. Carapace of female, seen from left side. X 40. 3. Carapace of female, seen from above. X 40. 4. Carapace of female, seen from front. X 40. 5. Secondary branch of lower antenna of female. X 210. 4. Additional Notes on Rhinoclemmys mexicana. By Dr. J. E. GRAY, F.R.S. &c. [Received April 3, 1871.] (Plate XXVIII.) In the 'Proceedings' of this Society for 1870, p. 659, I described a species of Rhinoclemmys, under the name of R. mexicana, from a specimen which we had received from M . Salle'; and in the month of November for the same year I figured the head of the animal (P. Z. S. 1870, p. 723, fig. 4 ). The specimen I first described appeared to have the normal colouring of the genus ; that is to say, the shell appeared to be of a nearly uniform dark colour above and below, with a pale margin forming a submarginal ring to the sternum. The specimen since I described it has been mounted and varnished ; and it now appears to be more olive-colour, slightly variegated with darker streaks and imperfect irregular paler rings ; and each of the dorsal shields is marked with a yellow spot, which I had not observed in any other species of this natural genus. W e have lately received from M . Boucard two other specimens of Emydes from Mexico with their heads; and, from the colouring of their heads, there can be no doubt (though the shells look very unlike the typical specimens of Rhinoclemmys mexicana) that they belong to the same species ; and in both of them the yellow spot in the centre of the areola is distinctly marked, being linear in the adult and large and circular in the young. And the colouring of the young explains the slightly variegated appearance of the typical adult specimen first described. The young specimen is olive-brown above, and pale yellow-brown, being darker in the central line of the sternum and over the sternal costal suture, below. The marginal shields are pale-spotted, and with a distinct pale semitransparent acute outer margin. The vertebral shields have two or three ovate concentric yellow rings, most distinct on the second and third, and an oblong central yellow spot, which is sometimes divided in half. The costal shields have two yellow subcircular rings, and a large yellow spot on the middle of the large areola. The head of this animal is coloured like that of |