4 GUIDES FOR VERTEBRATE DISSECTION 



back to the angle of the jaw, where it comes in close connection 

 with the squamosal already mentioned. This is a T-shaped bone, 

 one arm of the T articulating with the prootic, the other extend- 

 ing forward, above the pterygoid (better seen from the ventral 

 surface), until it nearly joins the maxillary. In addition to 

 these, portions of the vomers and pterygoids can be seen from 

 above, but their study is best undertaken from the ventral surface. 



Draw a dorsal view of the skull, X4, being careful to trace 

 exactly the limits of each bone; label all parts. 



Also draw the ventral surface of the skull on the same scale, 

 showing the exoccipitals, sphenethmoid, premaxillaries, maxillaries, 

 and quadrate jugals already seen as well as the following elements. 

 Beginning in the middle line behind, just in front of the exoccipi- 

 tals is an unpaired, sword-shaped parasphenoid bone, the guard of 

 which overlaps the prootics, the blade covering the sphenethmoid. 



From just in front of the sphenethmoid a palatine bone extends 

 laterally on either side to meet a palatine process of the maxillary, 

 while just in front of the palatines are a pair of irregularly shaped, 

 tooth-bearing vomers. With what bones do these last articulate? 

 The pterygoid bones are shaped like the Greek letter A- In front 

 they articulate with the lateral end of the palatines, the posterior 

 inner limb joins the prootic, the outer the squamosal at the angle 

 of the jaw. At the junction of squamosal and pterygoid is a 

 quadrate cartilage, to which the lower jaw is hinged. 



In a side view of the skull notice the gap in the bony wall of 

 the cranium between front o-parietals, sphenethmoid, and para- 

 sphenoid. See also the mode of articulation of maxillary and 

 quadratojugal. 



In the lower jaw make out an angulo-splenial bone extending 

 forward from the angle of the jaw on the inner and lower surface. 

 It bears on its posterior third a small coronoid process above, and 

 on its outer surface a groove for Meckel's cartilage. The upper 

 and outer surface of the jaw is composed of a dentary bone which 

 overlaps the angulo-splenial and extends forwards to meet a 

 pair of mento-Meckelian bones which touch at the symphysis of 

 the jaw. 



Draw a side view of the skull, X4. 



The Hyoid Apparatus, placed between and behind the halves 

 of the lower jaw, also belongs to the skull. It consists of a broad, 

 thin cartilaginous body with processes, anterior and posterior, for 



