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Show 2 5 6 Mil. F. E. BEDDAKD OX THE ANATOMY [June 6, 5. Some Notes upon the Anatomy of the Yellow-throated Lizard, G e r r h o sa u ru s f la v ig u la r i s . By F. E. Bf.ddard, F.R .S ., Prosector to the Society. [Received May 17, 1905.] (Text-figures 33-38.) Apart from osteology * and a few scattered notes, which will be referred to in the course of the present communication, there does not appear to be a great deal known about the internal structure of Gerrhosaurus. Inasmuch as this Lizard is regarded, from the point of view of external characters and osteology, as being exactly intermediate between the Lacertidte and Scincidae f, it seemed to me interesting to attempt a criticism or confirmation of this view, while recording any new facts which an investigation of Gerrhosaurus flavigularis might bring to light. Jugal Ligament. Many, but not all, of the Lacertilia possess, as is well known, a jugal ligament, which Huxley compared to the bony lower temporal arcade of Hatteria. The exact relationships of this ligament have not, I believe, been described in some of the Lizards in which I shall now proceed to detail the arrangement. It is possible to recognise several stages in the conditions of the jugal ligament, which may represent evolutionary stages, though it is, of course, not implied that the genera to be mentioned are genetically connected in the order named. In J guana tuberculata the ligament as a distinct structure is totally absent. On cutting through the skin covering the " cheek,"' the muscles and bones of this region of the skull are at once arrived at. It appeared to me, however, that the subcutaneous connective tissue, which is dense and white in most parts of the body, was rather denser and whiter in the region where the jugal ligament would be were it present. It is possible, in fact, that in this lizard an early stage is met with-that the ligament is not yet differentiated from the general connective tissue of the skin. On the other hand, it cannot be denied that the same fact may be explained on the theory that the ligament has disappeared. In any case, Gerrhosaurus offers an intermediate condition. In this reptile the ligament in question is anchored firmly to the quadrate behind, but in front it is not attached to the jugal bone but to one of the bony scales which cover the face in this region. That is to say, the ligament has not as yet completely detached itself from the skin. So, at any rate, the facts seem to indicate. It is important to notice in connection with the main object of the present communication, viz., to attempt to fix the systematic * Siebenrock, Ann. k. nat. Hofmus. Wien, vii. 1892. f Boulenger, Cat. o f Lizards. |