. Bulletin of the British Museum (Natural History), Geology. 254 REDFIELDIIFORM AND PERLEIDIFORM Skull (Fig. 9). The frontal is elongate, wide posteriorly and tapering towards the snout. It is sparsely covered with small tubercles. There are two pairs of parietals (parietal and postparietal of Wade). The anterior parietal is roughly oval, and bears three short rows of tubercles between which there were probably a pair of short sensory canals ( 218 and , Fig. 10). The posterior parietal is larger than the anterior parietal and is triangular, coming to a point ventrally. In latera
. Bulletin of the British Museum (Natural History), Geology. 254 REDFIELDIIFORM AND PERLEIDIFORM Skull (Fig. 9). The frontal is elongate, wide posteriorly and tapering towards the snout. It is sparsely covered with small tubercles. There are two pairs of parietals (parietal and postparietal of Wade). The anterior parietal is roughly oval, and bears three short rows of tubercles between which there were probably a pair of short sensory canals ( 218 and , Fig. 10). The posterior parietal is larger than the anterior parietal and is triangular, coming to a point ventrally. In lateral aspect this element is small, but its dorsal extent is in fact quite large. It bears small tubercles. The dermopterotic is extensive, forming the main lateral element of the skull roof; it too bears tubercles. The dermosphenotic is crescent-shaped and borders the postero-dorsal part of the orbit. Anteriorly it tapers to a point, but whether or not it meets the adnasal cannot be determined. It is thus possible that a small part of the frontal borders the dorsal edge of the orbit, though this is rather unlikely (see , Fig. 12). In Wade's reconstruction of B. gracilis (1935 : text-fig. 5) the opercular lies ventral to the suprascapular and the extrascapular (post-temporal and tabular of Wade). This reconstruction is the result of misinterpretation of specimens in which opposite sides of the skull have been relatively displaced. In fact the opercular lies further anteriorly than in Wade's reconstruction with the result that the skull appears shorter, and the inferred angle of the suspensorium appears steeper (, Fig. 10). The opercular is oval and slightly longer than broad. It bears a series of low concentric ridges which follow the outline of the bone. The subopercular is elongate, being 1-5 times as deep as, and slightly longer than, the opercular. It ro pmx. clav an Fig. 9. Brookvalia gracilis Wade. Restoration of skull and pectoral girdle, X5-5 Please n
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