OCR Text |
Show 1 7 2 DR. A. SMITH WOODWARD ON [June 7, to be interpreted as a partially ossified basioccipital element forming only an insignificant part of the occiput. The condyles themselves (c.) are convex and seem to have been covered with unossified cartilage, while they constitute the hindermost end of a pair of bones which enter extensively into the base of the cranium and also rise upwards to bound the foramen magnum on each side. These elements (ex.) therefore exhibit the same disposition as the exoccipitals of a frog, and must be homologous with the latter. They are pierced by the foramen for the vagus nerve, which is well seen on the left side. The posterior face ^ of each exoccipital immediately above‘the condyle is impressed with a triangular fossa, so that the upper end of the bone, partly obscured by matrix, has the appearance of bifurcating to unite in jagged sutures with the two bones which descend from the occipital row of roofing plates. The latter plates are evidently superficial in origin--either dermal or splint ossifications but there is no clear line of demarcation between them and the immediately underlying bones just mentioned. The inner half of Text-fig. 34. s i op eP socc Capitosaurus stantonensis; hinder view of occiput, restored, two-thirds nat. size. hocc., supposed basioccipital; c., occipital condyle on exoccipital; ep., epiotic; ex., exoccipital; fm., foramen magnum ; op., opisthotic ; psq., prosquamosal; pt., pterygoid; ptv., postero-temporal vacuity; qj., quadrato-jugal; qw., quadrate ; socc., space for supraoccipital; St., supratemporals. each plate of the median pair wrould directly overlap the cartilaginous supraoccipital; while its outer or lateral half alone is underlaid by the bone (ep.) which occupies the place of a piscine or amphibian epiotic. The inner two-thirds of each plate of the outer pair is underlaid by the second bone (op.) of triangular shape, which exhibits the usual relationships of an opisthotic. As shown on the right side of the fossil, the jagged suture between these two otic bones coincides exactly with that dividing the two overlying plates. The pterygoids unite in a deeply jagged suture with the broad basioccipital region, and then expand behind on each side into a vertical lamina (pt.) which articulates with |