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Show 1 9 0 4 .] LABYRINTHODONT SKULLS. 171 The sutures between the roof-bones in the hinder half of the skull are clear on both sides of the fossil; but the elements in the rostral region cannot be distinguished. There are the usual two pairs of small bones forming the occipital margin between the auditory notches, the middle pair being larger than the lateral pair. The parietal bones (pa.) are a symmetrical pair, twice as wide in their posterior half as in their anterior half, and truncated in front where they meet the frontals (Jr.). Their maximum width is less than their total length, and the pineal foramen is situated at their middle point. The frontals just enter the rim of the orbit at its antero-internal portion; but the parietals are completely excluded from this rim by the antero-posteriorly elongated postfrontals (ptf'.). The squamosal element (sq.) is longer than broad, articulating in front chiefly with the postorbital, but also meeting the postfrontal. The postorbital (pto.) forms the posterior and half the externo-lateral rim of the orbit; the jugal (j.) enters the outer portion of this rim ; while the prefrontal (prf.) completes it in front. The large prosquamosal (psq.) is about two-tliirds as deep as long, tapering to a point forwards. The quadrato-jugal (qj.) is about two-and-a-lialf times as long as deep, also tapering to a point forwards, and extending slightly downwards below the level of the tooth-bearing edge of the upper jaw. The jugal (j .), as usual, is irregularly triangular in shape, with the radiating ridges of its ornamentation predominant. At the rostral end of the fossil represented in Plate XI., the cranial roof and underlying matrix are removed to expose the palate from above. The antero-posteriorly elongated posterior nares (ptn.) are thus well seen ; and the hinder edge of the large premaxillary vacuity (pv.) is also preserved. The posterior limit of the premaxilla (pmx.) is distinct on the left side. The extensive vomerine plates (v.), divided by a median suture, are also well preserved. The premaxillary teeth, shown in transverse section, are small, uniform in size, and arranged in close series. The maxillary teeth, exposed in side view, are similar. Each tooth appears to have been a hollow cone with plicated walls. An excavation in the sandstone reveals hollows left by the decay of the usual large teeth, which occur on the palate in front of and behind the posterior narial openings. As already mentioned, the most interesting part of the skull is the occipital region, which is especially well preserved (fig. 2). It does not project sufficiently far backwards to admit of the occipital condyles being seen when the cranium is viewed directly from above. The position of the foramen magnum (fm.) is clear; while a vacant space (socc.) between this and the roof-bones of the occipital border suggests that a supraoccipital element was present but unossified. Below the middle of the foramen magnum there is a narrow tongue of bone (bocc.) separated by a little matrix from the prominent occipital condyles. This is probably |