SKELETON OF CETACEA. 425 



surface, where it is met by the frontals, ii, the overlapped parie- 

 tals coming into view only at the sides, where they expand into 

 the mastoids, s. The maxillaries, as they extend backAvard, rise 

 and expand, 21, covering so much of the frontals, n, as to allow 

 but a narrow strip of these bones to be seen, except where they 

 dilate to form the roof of the orbit. The nasals, 15, are oblong 

 tubercles set deeply in depressions of the frontal, at the back part 

 of the nostrils, e, e. The premaxillaries, 22, form the front and 

 sides of these apertures, save at the small portion contributed 

 by the maxillaries at g. The nasal passages descend almost 

 vertically. The malar is flattened where it helps to form the 

 orbit, and is covered by the maxillary : it sends backward a long 

 and slender process, which articulates with the zygomatic process 

 of the squamosal, and forms the only lower boundary of the orbit. 

 The bony palate has a deep longitudinal channel on each side in 

 some Dolphins. 



In the vertical section of the cranium of the Porpoise, fig. 287, 

 is shown the plane of the occipital foramen, 2, inclined from below 



287 



Section of skull, Porpoise. 



forward : the proportions of the inner Avail of the cranial cavity 

 contributed by the ex- 2, and super- 3, occipitals, by the alisphe- 

 noid, 6, the parietal, 7, the orbitosphenoid, 10, and the frontal, 11 : 

 the small vacuity between the alisphenoid and exoccipital is 

 blocked up by the loosely attached petrosal. The right nasal 

 passage is exposed, shoAving the proportion of the septum formed 

 by the vomer, 13, and the coalesced prefrontals, u : the vomer 

 extends forAvard to the middle of the upper jaAv, AA^hich is chiefly 

 composed of maxillary, 21, and premaxillary, 22. The small paka- 

 tines, 20, articulate Avith the vomer and maxillary, and send back- 

 Avard the larger pterygoids, 24, Avhich form with the vomer the 

 internal or loAver nostril, Avhilst the canal for the long conical 

 larynx is contributed by the pterygoids, 24, and a corresponding 

 descending plate of the basisphcnoid, 6, and basioccipital, 1. The 

 squamosal is excluded, as in Birds and loAver Vertebrates, from 

 the cranial cavity. The prefrontals in the Beluga {Deljjhln- 



