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Show MR. A. H. GARROD ON TOLYPEUTES TRICINCTUS. [Feb. 19, so well described its structure. Dr. Murie's figure, being based upon a photograph of the specimen, is thoroughly reliable. M. Is. Geoffroy St.-Hilaire has so well differentiated T. tricinctus and T. conurus that it will be necessary for m e only to mention that in the former there are five toes on the fore feet (as in the Society's specimen in m y possession), whilst in T. conurus, following the account of the discoverer of the species, there are " trois doigts seulement, avec le rudiment d'un quatrieme, aux pattes anterieures (ce rudiment represente le doigt interne). Point de doigt externe." The same remarks apply to T. muriei; for in the specimen in the British Museum there are four toes on each fore foot, whilst in Dr. Murie's example the pollex was not present. The tail, with its infundibuliform armature, is distally covered with four pairs of small rows of plates, arranged in longitudinal lines, there being one superior and one inferior pair, one supero-lateral and one infero-lateral. In T. tricinctus the whole organ is flattened from above downwards; in T. conurus and T. muriei it is not so. Two and a quarter inches appear to be its extreme length along its dorsal curve in all but the largest individuals, where it may reach two and a half inches. I do not find that the different species differ in the length of this appendage, which is correlated, as far as its length goes, with the length of the head, on the right side of which it always lies when the animal is rolled up1. I can find no important differences among the species in the anterior portion of the carapace. In the three free transverse semizones T. conurus and T. muriei agree, and differ from T. tricinctus in that the terminal or marginal lateral scutes of each zone (which with the scute above on each side of each zone are less tuberculated than the rest, to reduce the friction when the animal rolls itself up) are more detached from the second scute, are more rounded, and are smaller proportionately. In the posterior moiety of the carapace of T. conurus and T. muriei fifteen, sixteen, seventeen, or eighteen rows of scutes can be counted along the middle line from before backwards if the marginal scutes are included in the numeration; in T. tricinctus I never find more than thirteen or fourteen rows. In T. tricinctus only there is a triangular area composed of small scutes, with its apex directed downwards, and basally in contact with the cephalic shield, which interpolates itself between the eye and ear on each side. The following measurements of the specimens of the different species in the national collection may prove of service in determining the proportions of each. They demonstrate that the head is decidedly shorter than the anterior moiety of the carapace in T. tricinctus, whilst in T. conurus and T. muriei it is nearly always longer; that in T. tricinctus the head is more than half the length of the posterior moiety of the carapace, whilst in the two other species it is not so much as half that measurement. 1 Dr. Murie figures the tail on the left of the head (I.e.)-the photograph from which the drawing was made not having been reversed, most probably. |
