5b 



Journal of KinonioloK> and Zoology 



side of the anterior portion of the skull. Each is so placed that one 

 half of its surface articulates with the dorsal surface of the skull, 

 while the other half forms a portion of the side of the skull. 

 Through the center of the ectethnoid there is a dividing ridge which 

 separates its dorsal surface from its lateral surface. The dorsal 

 surface articulates anteriorally with the maxillary and the nasal, 

 and posteriorally with the frontal. The lateral surface articulates 

 anteriorally with the maxillary and posteriorally with the frontal ; 

 a small portion remains between the.se two articulations and this 

 l^ortion bounds part of the opening into the olfactory fossa. 



The maxillaries (4) are long slender bones, which, together 

 with the premaxillaries bear the teeth of the upper iaw. The 

 maxillary articulates only anteriorally and diverges posteriorally to 

 form a long rather slender process extending al)out one-half the 

 length of the skull. Before the maxillary articulates with the main 

 body of the skull it diverges on the inner side into two portions; 

 the upper portion articulates with the dorsal l)ones of the skull, 

 while the lower portion articulates with the ventral bones. The 



hollow depression resulting from these two divergences forms the 

 opening into the olfactory fossa. Dorsally the maxillary articu- 

 lates with the nasal and the ectethnoid; and ventrally with the pre- 

 maxillary and the squamo-iialatine. 



The frontals (,5) form a little less than one-half of the dorsal 

 surface of the skull. They lie in contact with one another for about 

 two-thirds of their length, diverging anteriorally to form a pair of 

 short prcmaxillary proce.sses, and diverging itosteriorally 1o form 

 two processes, — a blunt rather broad parietal i)rocess and a long 

 slender i)rocess which articulates with the sijuamosal bone. On the 

 ventral surface of each frontal is an out curving ridge which serves 

 for the attachment with the sphenethnoid. 



