36 PROFESSOR OAVEX ON INDIAN CETACEA. 



the temporal fossa (ib. t), undcrlapping the squamosal (ib. 27), and thinning-ofF to its 

 outer margin : its anterior border is notched by the intersphenal fossa (tr) : 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 (tr), 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 (PI. XII. & PI. XIII. 

 fig. 2, t) is 1" Y" in antero-postcrior, and 2" in transverse extent, has its marginal 

 boundary almost completed by the approximation of the postfi-ontal (ib. 12) to the zygo- 

 matic part of the squamosal (ib. 27), the distance between their free ends being but 6'" ; 

 but the zygoma terminates on a lower level (PI. XII. fig. 1, 27]. 



The presphenoid (Pis. XIII. & XIV. fig. 2,9) retains its distinction fi-om the basi- 

 siihenoid (5), but has coalesced with the orbitosphenoids (10), as have these with the 

 alisphenoids (s). 



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 (PI. XIV. fig. 2, n) : the orbito- 

 sphenoids expand and ascend to form with the coalesced frontals the anterior waU 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, tr), 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 Phoccena hrevirostris. The roof of the orbit is unbroken, gently con- 

 cave from before backward, formed chiefly by the frontal (PI. XII. fig. 1, 11, n), which is 

 notched near the middle of the superorbital ridge: this is tliick, obtuse, and produced 

 backward and downward into a postfrontal or postorbital process (ib. 12). Above the ridge, 

 the fr-ontal (ib. u') 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 (ii') ife ob- 

 tuse, and thickens to join the malar (26), fi-om which it is partly divided by a notch^. 



' " 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 ou 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 alisphcnoid in a groove anteriorly." — Phi/seter macrocephalus, op. eit. 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 ate ; the under and anterior 

 part is overiapped by the vomer."— PA^seter inacrocephalus, op. cit. p. 447. 



The frontals are large triangular plates, concave externally, with the outer and fore angle produced into 



