On a New /Species of Scymnognathus (S. tigriceps). 29 



The pterygoids are large bones. They form behind part of the 

 median descending ridge. Postero-laterally a process is sent to 

 meet the quadrate and also to support the columella cranii. Each 

 pterygoid also forms a huge descending pterygoid process. In front 

 the development of the pterygoid is slight. It meets the trans- 

 palatine and the palatine. Superiorly the pterygoid forms a large 

 thin paramedian plate not unlike that seen in the pterygoid of the 

 Pelycosaurs. The huge median bony septum is probably formed by 

 the two pterygoid plates anchylosing with a median plate formed by 

 the basisphenoid or ethmoid. In section no sutures can be made out, 

 but the outer wall of the septum is unquestionably pterygoid. In 

 the allied Scylacognathus parvus the pterygoids have probably had 

 cartilage between them, as they are not anchylosed to form a septum. 



The palatines form a large part of the palate, and send up para- 

 septal plates, as do the pterygoids. 



The vomer is a true median vomer, as in the Anomodonts, the 

 Cynodonts, and Mammals. It is a large thin plate which divides 

 the nasal space into two. The greater part of the bone is thin, but 

 the lower border which formed part of the roof of the mouth is 

 fairly strong and bmid. 



There appears to be no trace of paired prevomers. 



The quadrate is fairly large, and in its relations to the squamosal 

 not unlike that of the Cynodonts, but relatively very much larger. 

 There appears to be no trace of a quadrato-jugal. 



The stapes is long and fairly strong. 



The lower jaw is in beautiful condition, and all the elements can 

 be satisfactorily made out. 



The dentary is as usual the largest bone. It has a very powerful, 

 deep symphysis. It is not yet known for certain, but it seems not 

 improbable, that all those supposed Therocephalians with a powerful, 

 deep symphysis will prove to be Gorgonopsians. It is pretty certain 

 at any rate that those carnivorous Therapsida with a feeble, loose 

 symphysis are true Therocephalians. The coronoid process is 

 fairly well developed, but shorter than in typical Therocephalians. 



The splenial is large. It forms much of the lower part of the 

 symphysis and most of the inner side of the front half of the jaw. 



There is a distinct coronoid bone. It is a thin triangular splint 

 that supports and holds together parts of the dentary, the surangu- 

 lar, the angular, and the prearticular. 



The angular is the second largest bone of the jaw. In front it 

 passes between the splenial and the dentary, and extends nearly to 

 the symphysis. Posteriorly it forms most of the lower half of the 



