. Bulletin of the British Museum (Natural History), Geology. ICHTHYOKENTEMA PURBECKENSIS 21 The premaxilla (pmx., PL 2, fig. 5) (P. 8379 ; P. 44956) is a small, roughly tri- angular bone bearing about ten teeth in a single row along its oral border. The premaxillae did not meet in the mid-line, but were separated by the rostral. A small notch on the medial edge of the premaxilla articulated with a projection on the lateral edge of the rostral. A projecting facet in the centre of the dorsal edge of the premaxilla articulated with the antero-ventral corner of the antorbital. The maxilla (mx.) (P
. Bulletin of the British Museum (Natural History), Geology. ICHTHYOKENTEMA PURBECKENSIS 21 The premaxilla (pmx., PL 2, fig. 5) (P. 8379 ; P. 44956) is a small, roughly tri- angular bone bearing about ten teeth in a single row along its oral border. The premaxillae did not meet in the mid-line, but were separated by the rostral. A small notch on the medial edge of the premaxilla articulated with a projection on the lateral edge of the rostral. A projecting facet in the centre of the dorsal edge of the premaxilla articulated with the antero-ventral corner of the antorbital. The maxilla (mx.) (P. 1073 ; P. 44957) is rather short, and ends below the centre of the orbit. The bone bears a single row of teeth which extends along the entire length of its oral border. The rod-like head of the maxilla inclines medially at about 45 degrees to the body of the bone, and articulated with a facet at the base of the wing of the vomer. The premaxilla lay below and in front of the head of the maxilla. A slight thickening of the dorsal surface of the lateral part of the head of the maxilla marks the articulation of the maxillary process of the palatine. The maxilla is unornamented. ang. 'Ymond. Fig. 8. Ichthyokent&ma purbeckensis. Reconstruction of left mandible in lateral view. Based mainly on P. 44973-75 and P. 45031. For explanation of lettering see p. 43. The single supramaxilla (smx.) (P. 7807 ; P. 3607 ; P. 44958) is an elongated slip of bone, pointed anteriorly, whose curved ventral edge fits against the dorsal part of the posterior half of the maxilla. (d) Mandible The lower jaw is composed of four elements : the dentary and angular, which together form the entire external or labial surface of the mandible ; the Meckelian bone ; and a single small coronoid (Text-figs. 8, 9 ; PI. 4, fig. 9). The dentary (den.) is the largest of these four bones. It is gently curved in the vertical plane so that the inner surface is concave and the outer convex ; in addition the anter
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