80 PRACTICAL ZOOLOGY. 



pharyngeal teeth- The bones supporting these 

 teeth, above and below, are the pharyngeal bones; 

 they represent a fifth gill-arch. Again depress and 

 raise the lower ends of the gills, observing how the 

 pharyngeal teeth are brought together. What is 

 the probable use of these teeth, and what is the work 

 done by the teeth previously examined ? 



Again examine the gill-rakers, and observe how 

 they are affected by bending and straightening the 

 gill-arches. Examine the bone which bears the 

 branchiostegal rays, and note with what bones it is 

 connected. 



12. Examine the bones in the posterior border of the gill- 

 opening; these are together called the pectoral arch. 

 The largest of these bones is the clavicle; its upper 

 part forms a projection above the base of the pectoral 

 fin. Connected with the upper end of the clavicle is 

 the supra-clavicle, which, in turn, is connected with 

 the skull through the post-temporal. Cut away the 

 flaps of the body-wall bearing the fins. 



13. Note also the bones supporting the ventral fins ; these 

 are considered as representing the pelvis. In the 

 higher fishes the pelvis is fastened to the clavicle ; in 

 the lower fishes it is separate from the rest of the 

 skeleton and imbedded in the flesh. How is it in 

 the specimen you are studying? Carefully remove 

 the ventrals, with the bones which support them ; ex- 

 amine and describe them, after scraping away all 

 muscles and other soft tissues. 



If the dissection of the muscles and the brain are 

 not to be made at this time, carefully cut away the 

 gills at their upper attachment, and remove them ; 



