. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 188 ANNALS OF THE SOUTH AFRICAN MUSEUM. Fig. 25. LystrosauTus curvatus. Nat. Mus. No. Premaxillary portion of palate in ventral view. the premaxilla overlaps the anteroventral corner of the diverging vomerine wing. In this way a very firm, interlocking suture is formed between the premaxilla and vomer (Figs 28, 35). The relative extent of the maxilla varies with the size of the premaxilla. It meets the latter bone anteriorly, the septomaxilla and lacrimal dorsally, and overlaps the jugal poste
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 188 ANNALS OF THE SOUTH AFRICAN MUSEUM. Fig. 25. LystrosauTus curvatus. Nat. Mus. No. Premaxillary portion of palate in ventral view. the premaxilla overlaps the anteroventral corner of the diverging vomerine wing. In this way a very firm, interlocking suture is formed between the premaxilla and vomer (Figs 28, 35). The relative extent of the maxilla varies with the size of the premaxilla. It meets the latter bone anteriorly, the septomaxilla and lacrimal dorsally, and overlaps the jugal posterodorsally. Ventrally it is extended as a strong canini- form process which carries the single canine tusk, while a posterior process extends as part of the zygomatic arch to below the middle of the orbit. The line of the zygomatic arch is prolonged downwards to the caniniform process as a pronounced lateral thickening of the snout, the tusk and surrounding portions of the palate being thus powerfully buttressed by the entire zygoma. The lateral thickening of the snout has a rough, pitted surface, suggesting a covering of horn extending up from above the tusk. The posterior part of the sharp palatal rim is formed by the ventral edge of the maxilla in front of the tusk (Figs 24, 26). This, the sharpest part of the palatal rim, slopes down and back to lie flush against the inner surface of the tusk, and is always well deve- loped, regardless of tusk size. In the palate the maxilla separates the premaxilla from the palatine and *orms the lateral border of an anterior notch in the choana. Laterally to this it covers the palatine and the anterior palatal process of the pter^'goid by its posterior pterygoid process, the anterior part of which forms the ventral border of the labial fossa (Figs 24, 31). In the region of the maxillo-palatine contact in the palate, at the base of the caniniform process, the surface of the maxilla is pitted and scored by grooves similar to those found on
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
