472 
SIR R. OWEN ON THE FOSSIL REMAINS OF TWO SPECIES 
The subject of figs. 1-2 (Plate 29) is the occipital and basi-sphenoidal part of the 
skull, showing the reptilian character of a single occipital condyle. Of this specimen 
the marginal portions, 2, 2, fig. 1, supplied by the ex-occipitals are slightly convex; the 
larger proportion (ib., l), due to the basi-occipital, is more feebly concave; but the 
sutures, still discernible in the corresponding part of Megalania prisca* are 
obliterated, and the shape of the condyle is semicircular, not elliptical. Its breadth is 
33 mm., its height is 22 mm. 
The outlet of the brain case (foramen magnum, ib., n) is of equal size to that in the 
larger genus, and is elliptical, not circular. Its vertical diameter is 25 mm., its trans¬ 
verse diameter is 23 mm. 
The confluent side extensions of the occiput, formed by the basi-, ex-, and par- 
occipitals, constitute a massive extent of bone (ib., 4, p) 2 inches in vertical diameter 
and 1-| inches transversely. The part directed downward (p) and extending below 
the condyle is divided by a large irregular cavity (x) from the transverse cuboidal mass 
(4) above. The super-occipital spine or ridge (n s ) is sharper than in Megalania prisca 
(fig. cit.) ; its summit, showing a broader base, is broken off. The breadth of the occiput 
is 4 inches 8 lines (100 mm.), its height 2-^ inches (65 mm.). 
The cranial cavity at the fore part of this segment (Plate 29, fig. 2, n) of the skull 
gives 30 mm. in the transverse, 35 mm. in the vertical diameter. The portions of 
cranial wall continued forward from the sides of the brain case are thin, not exceeding 
2 mm. The roof of the brain case here preserved is impressed by a transverse semi¬ 
circular canal or sinus (s) 3 mm. in diameter. The lower border of the anterior 
fracture shows the canal leading down to the recess (r, fig. 2) lodging the pituitary 
remnant of the primitive pharyngeal tract. Half-way between the fore and hind 
apertures of the brain case a small tuberosity (t) rises from the middle of the floor. 
Behind this, w r here the side wall rises from the floor, are two small orifices, leading 
each to a canal which has its outlet (fig. 1, u) at the base of the ex-occipital. 
In advance of these intracranial foramina is the entry of a larger canal leading to an 
irregular cavity (fig. 1, x), widely opening, in the present mutilated fossil, at y (fig. 2) 
upon the under part of the broad and deep par-occipital process, p. From this cavity 
or chamber a canal, 12 mm. by 10 mm. diameter, leads obliquely inwards and 
forwards (fig. 2, y) towards the wall of the pituitary chamber. The under surface of 
the basi-occipital is concave, expanding as it descends and advances. Its junction, 
and here coalescence, with the basi-sphenoid is indicated by a pair of ridges which 
diverge from near the mid-line outward and backward. The par-ex-occipitals (4, 4) 
are sub-quadrate masses, terminated each by a hemispheroid cavity with a thin sharp 
border. Each ex-occipital is excavated behind and below by the chamber, into which 
opens the canal from the larger of the three foramina on each side of the occipital 
division of the cranial chamber. A large foramen (fig. 1, m) on the upper and forepart 
of the ex-occipital leads also to the sinus (x), from which cavity is continued a wider 
* ‘Phil. Trans.,’ 1880, vol. 171, Plate 36, figs. 1 and 2. 
