ABT. 28 SKULL OF ZARHAOHIS FLAGBLLATOE KELLOGG 13 



palatine are clearly outlined. It is a relatively narrow bone mortised 

 into the maxilla above and bounded externally by the upper margin 

 of the external reduplication of the pterygoid. As now understood, 

 each pyramidal cavity is inclosed on the rear by the internal plate of 

 the pterygoid, on the outside by the external reduplication of the 

 pterygoid, on the inside by a thin internal plate of the pterygoid 

 posteriorly and by the vomer anteriorly, and above by the palatine 

 posteriorly and the maxilla anteriorly. The thin internal plate of the 

 pterygoid does not project as far forward as in Platanista, but other- 

 wise the relations between the palatines and pterygoids are essen- 

 tially the same in both genera. The external reduplication of the 

 pterygoid is not developed on skulls of Inia and Lipoies, thus ex- 

 posing the entire alisphenoid. On the ZarJiachis skuU the oxtromity 

 of the alisphenoid is not overspread by the external reduplication of 

 the pterygoid and it appears within the temporal fossa in the sanie 

 relative position as in hiia. In Platanista the extremity of the ali- 

 sphenoid is overspread by the external reduplication of the pterj^goid. 



The keel of the trough of the vomer is exposed between the nasal 

 passages and the anterior extremity of the external reduplication of 

 the pterygoid. In its shape and relations with the surrounding 

 bones, the vomer does not differ from that on the first skull. It ex- 

 pands horizontally posterior to the na^sal passages, but terminates 

 near the anterior margin of the basisphenoid. 



The median region of the basicranium. is rather broad, bounded on 

 each side, as mentioned above, by a continuous wall formed by the 

 vaginal plate of the pterygoid and the adjoining falcate process of the 

 basioccipital. The surface of the median area between these sloping 

 walls is more or less concave. The basioccipital is a much larger 

 bone than the basisphenoid; the transverse suture between these 

 bones is unusually distinct. The occipital condyles are large and are 

 separated mesially by a deep groove. A deep jugular incisure ap- 

 pears between the internal margin of the exoccipital and the posterior 

 ihargin of the falcate process of the basioccipital. A small condylar 

 foramen is present on each side between the base of the falcate process 

 of the basioccipital and the condyle. 



The body of the squamosal contributes a part of the lateral wall of 

 the brain case and its lateral projection or zygomatic process serves 

 as the articular surface for the condyle of the lower jaw. The gle- 

 noid articular surface on the zygomatic process curves upward and 

 forward and is concave from side to side. The external border of 

 the zygomatic process is prolonged downward, forming a thin crest; 

 the internal border is rounded ojff. The postglenoid process is short 

 and curves forward. A shallow groove for the external auditory 

 meatus traverses the squamosal behind the postglenoid process. A 

 narrow posteriorly directed process of the squamosal is suturally 



