ART. 26 REMAINS OF FOSSIL PORPOISES KELXrOGG 19 



The distinguishing features of the squamosal are the large size and 

 strength of the zygomatic arch, the short robust postglenoid process, 

 and the slender glenoid process which is directed forward and down- 

 ward in front of the tympano-periotic recess. A narrow groove for 

 the external auditory meatus traverses the squamosal behind the 

 postglenoid process. To the inside of the postglenoid process and in 

 a position corresponding to the direction of this groove, the periotic 

 was attached to the skull, and it in turn with the tympanic. The 

 posterior border of the squamosal articulates with the exoccipital 

 and between this suture and the transverse groove for the external 

 auditory meatus, a rounded tuberosity is formed. The zygomatic 

 process of this skull is rather large and has a slight outward curve. 

 The lower surface is convex, with a decided upward and forward 

 curve. Tlie articular surface for the condyle of the mandible is an 

 oval concavity, looking forward, inward, and downward. Internal 

 to the glenoid fossa there is a sharply defined longitudinal depres- 

 sion, wide posteriorly and narrow anteriorly, which commences in 

 front of the groove of the external auditor}^ meatus and extends for- 

 ward to the anterior margin of the squamosal.- The lower margin 

 of the squamosal, internal to this last-mentioned fossa, is prolonged 

 downward and inward to form a thin plate. 



In this skull the line of separation between the exoccipitals and 

 the basioccipital crosses the falcate process of the latter. Posteriorly, 

 the exoccipitals are somewhat concave. The paroccipital process is 

 relatively thick, its anterior aspect is roughened, and internally in 

 conjunction with the descending plates of the basioccipital forms an 

 incisure for the passage of the jugular vein. 



Measurements of the akull 



mm. 



Total length (occipital condyles to extremity of rostrum) — 1 1,066 



Length of rostrum (maxillary notches to tip of beak) 859 



Breadth of skull across zygomatic processes of squamosal 240 



Height of skull (between tip of descending process of basioccipital 



and nasals) 160 



Height of skull (basisphenoid to nasals) 123 



Greatest breadth of skull across supraorbital processes 236. 5 



Occipito-premaxillary length of skull (posterior margin of maxilla to 



tip of rostrum) 1,000 



Greatest distance between outside margins of premaxillae opposite 



nasal passages S9 



Greatest breadth of right premaxilla in front of nasal passages 30 



Greatest breadth of left premaxilla at maxillary notch 27. 5 



Breadth of rostrum at maxillary notches 108 



Greatest breadth of rostrum at extremity 1-1 



Length of frontal plate of right maxilla 162 



Greatest breadth of right maxilla posterior to nasals 66. 5 



