102 RECORDS OP THE AUSTRALIAN MUSEUM. 



The exoccipitals (Plate ix., fig. 1, exoc.) are invisibly fused 

 with the prootics laterally and dorso-laterally. Ventrally they 

 are almost separated by a backward projection of the parasphenoid, 

 which bone also bounds them anteriorly on the ventral surface. 

 Dorsally they are almost separated by an endosteal rudiment of 

 the supraoccipital (PI. ix., fig. 1, so.). The occipital condyles 

 (oc. con.), are situated latero-inferiorly and have the smooth 

 articulating surfaces produced anteriorly on the ventral edge. 

 They are separated from one another by a space equal to one and 

 three-quarters their diameter. External to the condyles and 

 piercing their peduncle, is a large, single foramen for the passage 

 of the ninth and tenth nerves (iV. 9, 10). 



The prootics (pro.) are fused with the exoccipitals and present 

 no sutures with these bones. Antero-mesially on the dorsal 

 surface they lie in contact with the frontoparietals, and are 

 covered ventrally by the lateral wings of the parasphenoid. The 

 auditory capsules are distinctly sculptured above, showing 

 externally the positions of the semi-circular canals. The anterior 

 semi-circular canal (PI. ix., fig. 1, a.s.c.) shows externally as a 

 rounded ridge lying in contact with the frontoparietal, and 

 directed backwards and inwards. It is directly continuous 

 behind with the posterior semi-circular canal (PI. ix., fig. 1, p.s.c), 

 which runs outwards, backwards and downwards. The horizontal 

 semi-circular canal (h.s.c.) runs above the fenestra ovalis, forming 

 the prominent lateral ridge of the capsule. The upper face of 

 the capsule is broader than the lower and bevels away to a 

 narrow base supported by the lateral wings of the parasphenoid, 

 so that none of the three foramina which pierce the prootic 

 laterally are visible from above. The foramen ovale (PI. ix., 

 fig. 2, f.o.) is large, situated nearer the ventral surface than the 

 dorsal, and bordered above by the ridge formed by the horizontal 

 semi-circular canal. Anteriorly each prootic is pierced by a 

 single aperture for the transmission of the fifth and seventh 

 nerves (N. 5, 7). 



The frontoparietals ( frp.) are considerably longer compared 

 with their total width than in Chaperina J'nsca, the respective 

 measurements being, Austrochaperina three-tifths as broad as 

 long, Chaperina six-sevenths as broad as long. The suture with 

 the nasal is shorter than in Chaperina, while the edge of the 

 nasal in contact with the ethmoid is of greater extent. Between 

 the two pairs of bones, nasals and frontoparietals, is a diamond- 

 shaped space enclosing part of the ethmoid. The fontanelles are 

 paired and separate. The frontal fontanelles (PI. ix., fig. l,J.fon.) 



