a large bone enclosing the anterior third of the brain case. (3) 

 Palatines slender bones ventral to the nasals, (on the roof of the 

 mouth), passing outward from near the anterior end of the parasphe- 

 noid to the ma: illae. (4) Vomers two irregular bones anterior 

 to the last and bearing teeth fas do the premaxillae and maxillae. (5 ) 

 Pter\goids: a tri-radial bone on each side attached to anterior wall of 

 auditory capsule, to the squamosal and to the inner side of the 

 maxillae. (6) The Mandible or lower jaw made up of a right and 

 left half or ramus, each of which has a main piece (angulo-splenoid) 

 extending from the auditory region and covered anteriorly by a 

 scale-like external bone (dentary) and also a short nodular piece 

 (mento-Meckelian ) at its anterior tip where it joins its fellow 

 ramus in the median line. 



c. (i) In a slightly boiled or fresh skull remove carefully the 

 membrane or investing bones with forceps or scalpel and draw the 

 chondro-cranium that is thus laid bare, together with the following 

 bones that remain as ossified parts of the cartilaginous skull: First, 

 exoccipital ; second, pro-otics ; third, sphenethmoid ; fourth, quadrate ; 

 fifth, mento-meckelian. (2) This cartilaginous skull forms a case 

 for the brain, olfactory and auditory organs; on each side a long 

 sub-ocular arch or palato-qnadrate cartilage standing out a\vay from 

 the cranium is produced as a snspensorimn at its posterior end 

 for the articulation of the mandible; the latter is Mcckd's cartilage, 

 ossified at its anterior tip as the mento-Meckelian bone. (3) Xote 

 the fontanelles or imperfect parts of the roof of the cranium; the 

 foramina for passage of nerves from the brain through the chondro- 

 cranium ; the partly ossified coluniella aitris extending from the tym- 

 panum to an opening, fenestra oi'alis, in the auditory capsule. 



d. The hyoid : this consists of a broad flat body of cartilage in the 

 floor of the mouth, and of four pairs of processes, (i ) The anterior 

 cornua arising from the anterior edge of the body on each 

 side as long slender cartilaginous rods attached near the fenestra 

 ovalis. (2) Posterior coma or thyro-hyals; a short thick bony piece 

 joined on each side to the posterior edge of the body near the middle 

 line. (3) On each lateral edge anteriorly and posteriorly (or at the 

 angles of the body), a short rounded cartilaginous process. 



Draw tJie hyoid. 



VI. MUSEUM SPECIMENS. 



Observe in the Museum, central section, numerous skeletons of 

 vertebrates, and compare the bones of the appendages with those you 

 have studied in the frog. 



66 



