XIII.] THE FROG. 209 



side of a median suture which answers to the 

 sagittal and frontal sutures in man. 



b. In front of these come two triangular bones 

 the nasals. 



c. In front of the nasals are two- other bones, which 

 belong rather to the ventral than to the dorsal 

 face of the skull. They form the extreme front 

 of the snout, and each sends a process towards 

 the nasals ; these are the premaxillary bones. 



3. The lose of the skull. 



a. Running along the greater part of the floor of 

 the cranial cavity, from the occipital foramen 

 to the vomers, is a bone shaped like a dagger 

 with a short handle and a strong guard. The 

 latter spreads out under the pro-otics. This is the 

 parasphenoid bone. 



b. Appearing at the base of the skull, at the front 

 end of the parasphenoid, is the girdle-bone or 

 sphenethmoid (which represents several bones 

 joined together) ; this bone closes in the floor and 

 sides of the forepart of the cranial cavity and 

 also its roof, being concealed in the latter place 

 by the anterior ends of the parieto-frontals. The 

 sphenethmoid has a single cavity behind, which 

 enters into the formation of the cephalic chamber, 

 and two cavities in front, one for each nasal 

 chamber, separated by a septum. 



o. f Running out transversely from the girdle-bone 

 and the anterior end of the blade of the para- 

 sphenoid on each side, is the slender palatine. 

 M. 14 



