36 



PROF. D ARCY W. THOilPSOJf OS THE 



[Jan. 17, 



nteiTupted ; the posfcfrontal process is larger and arches down- 

 wards ; the squamosal process is very stout, and it^ outer surface 

 is practically continuous with that of the low, broad, suprameatal 

 process. The auditory meatus is wide open and nearly square ; 

 the basitemporal plate is much smaller relatively, and scarcely 

 larger actually than in Geoffroyus ; and the surfaces lateral to 

 it are correspondingly broad. The two heads of the quadrate are 

 confluent ; the anterior or pterygoid process of the same bone is 

 unusually large. The mandibular fontanelle is obsolete. The 

 intraorbital fissures are unusually small. 



Fig. 34. 



Pyrrhdopds personatn. 

 Fig. 35. 



Auditory region of Pyrrhulopsis. 



Pi/7-rJiulo2?sis, Aprosmictus, and Polytelin differ from Tanygnallms in 

 several points, and particularly in the region of the postorbital and 

 squamosal processes. The postorbital is very indistinctly defined, 

 and exists only as the thickened edge of the descending posterior 

 rim of the orbit, where it meets the temporal fossa. It descends 

 lower mAprosmictus than in Pyrrhulopsis,and lower still in PolyteUs, 

 where it leaves only a slight and narrow groove between it and the 

 squamosal to represent the outlet of the fossa. The configuration 

 of the base of the squamosal process is totally different from that 

 of Tanygnathus ; for the suprameatal process is now separated by 

 a wide and deep groove from the squamosal, and the latter does 



