6 PROFESSOR OWEN ON INDIAN CETACEA. 
(ah) 
the temporal fossa (ib. ¢), underlapping the squamosal (ib. 27), and thinning-off to its 
outer margin: its anterior border is notched by the intersphenal fossa (#7): there is no 
distinct foramen ovale. It supports the natiform protuberance of the cerebrum, and is 
divided from the orbitosphenoid (ib. 10) by the intersphenal fissure (¢r), from which 
two channels lead toward the back part of the orbital roof (or), blending together 
and widening as they grow shallow!. The temporal fossa (Pl. XII. & Pl. XU. 
fig. 2, t) is 1” 1” in antero-posterior, and 2” in transverse extent, has its marginal 
boundary almost completed by the approximation of the postfrontal (ib. 12) to the zygo- 
matic part of the squamosal (ib. 27), the distance between their free ends being but Gms 
but the zygoma terminates on a lower level (Pl. XI. fig. 1, 27). 
The presphenoid (Pls. XIII. & XIV. fig. 2,9) retains its distinction from the basi- 
sphenoid (5), but has coalesced with the orbitosphenoids (10), as have these with the 
alisphenoids (6). 
The orbitosphenoid (ib. 10) has its posterior boundary partially defined by the inter- 
sphenal fissure, at the fore part of which the optic canal is marked off by an intercranial 
process arching over the same downward and backward (Pl. XIV. fig. 2,2”): the orbito- 
sphenoids expand and ascend to form with the coalesced frontals the anterior wall of the 
cranial cavity ; the optic channel extends forward and outward from the intersphenal fissure, 
and, blending with the trigeminal one (PI. XIII. fig. 2, #7), is lost on the roof of the 
orbit (ib. or)?. The fossa (ib. d), into which the foramina on the frontal or nasal plate of the 
maxillary opens, is in advance of the optic channel (ib. 10). There is no intraorbital fossa 
answering to that in Phocena brevirostris. The roof of the orbit is unbroken, gently con- 
cave from before backward, formed chiefly by the frontal (Pl. XII. fig. 1,11, 11’), which is 
notched near the middle of the superorbital ridge: this is thick, obtuse, and produced 
backward and downward into a postfrontal or postorbital process (ib. 12). Above the ridge, 
the frontal (ib. 11’) contracts; its surface is here free from the maxillary (21’), is slightly 
concave vertically, before it is reduced by the overlapping of the parietal (7) and superocci- 
pital (3) behind, and of the maxillary ( 21’ ) in front, to the narrow strip (11), which rises, 
bending convexly, to the vertex. The fore part of the superorbital ridge (11) is cb- 
tuse, and thickens to join the malar (26), from which it is partly divided by a notch®. 
1 « The basisphenoid, or thick hexagonal bone, concave from side to side below, nearly flat above, is anchylosed 
to the alisphenoids: these are perforated near the middle of their base by the foramina ovalia and rotunda, 
have a thick quadrate plate on their inner side, forming their entocranial surface: they extend into a point 
anteriorly, and articulate both with the frontal and with the parietal angle of the superoccipital. The 
squamosal receives the alisphenoid in a groove anteriorly.” —Physeter macrocephalus, op. cit. p. 442. 
* «The presphenoid and the anchylosed orbitosphenoids form the anterior wall of the cranial cavity, and are 
perforated by the optic foramina: they articulate anteriorly with the frontal, sending up a small process into 
the interspace at the beginning of the frontal suture, which process is impressed by a fossa in each of its 
sides: the posterior and lateral parts of the orbitosphenoids unite with the great ale; the under and anterior 
part is overlapped by the vomer.”—Physeter macrocephalus, op. cit. p. 447. 
* “The frontals are large triangular plates, concave externally, with the outer and fore angle produced into 
