510 Mr. D. M. S. Watson on the Cynodont'ia. 



Finally, the squamosal runs forward along the upper edge 

 of the zygoma for some distance. The whole squamosal 

 region is rounded, differing markedly from its contour in 

 Gomphognathus. 



The jugal is a large bone, forming the whole of the lower 

 margin of the orbit, and sending a long, very strong, process 

 back below the postorbital and squamosal to form the major 

 pait of the zygoma. Below the orbit the lower border of the 

 jugal is carried down to form a low process much roughened 

 by muscle-insertions, which is homologous with a much 

 larger process in Cynoynathus and Gomphoynathns. This 

 process is presumably associated with the musculature of the 

 lips. 



The maxilla is, as always in Cynodonts, a large deep bone 

 extending forward with its upper edge in contact with the 

 jugal, lachrimal, nasal and septomaxilla to a sutural overlap 

 on to the premaxilla. 



The premaxilla is only incompletely preserved, the outer 

 wall of the alveoli and the internarial process being broken 

 away. 



The septomaxilla is a relatively large bone lying on the 

 anterior border of the maxilla and excluding that bone from 

 any participation in the nostril. It forms a small exposed 

 area on the face, extending inwards as a vertical plate of 

 bone for some distance ; the anterior surface is depressed 

 into a conical pit, bounded externally by the maxilla ; 

 between the two bones is a small foramen, not visible from 

 the side, which is the last remnant of the septomaxillary 

 foramen, which is shown by comparison with Fawcett's 

 figures of Tatusia to be probably for the passage of the 

 ductus naso-lachrimalis. 



The septomaxilla has a small upstanding process at its 

 lower end, but appears to lack the customary process at the 

 middle of its height. 



Quadrate. — The quadrate complex is a small bone visible 

 only from behind through the notch in the lower part of the 

 squamosal. It is clearly divided into two parts — an inner 

 (the quadrate) and an outer attached only to the lower edge 

 of the quadrate and separated from it above by a groove 

 ending in an enlarged foramen ; this element is the quadrato- 

 jugal, here recognized for the first time in a Cynodont. 



It is clearly shown by the specimen that the outer edge and 

 upper end of the notch in the squamosal are moulded on the 

 quadrato-jugal, the lower part of the inner border of the 

 notch, which is so cut out as to produce an incipient division 

 into two, bearing a similar relation to the quadrate. 



