ANATOMY OF VERTEBRATES. 



105 



23, and external to it the pterygoid abutting upon the hypotym- 

 panic, 28 d : between this and the epitympanic, 28, are the 

 mesotympanic, 38, and the pretympanic b. The preopercular, 34, 

 runs parallel with, strengthens, and connects together the divisions 



12 



11 



Base of the skull with left side of mandibular arch and its orercular appendage, Perch (Perc a fluviatilis) 



of the tympanic pedicle : it supports the opercular, 35, the sub- 

 opercular, 36, and the interopercular, 37. In the mandibular 

 ramus the articular is marked 29, and the dentary 32. The free 

 end of the maxillary is seen at 21. 



In fig. 85 the maxillary and mandibular arches and appendages 

 are removed, the stylohyal, 38, having been detached from the 

 epitympanic. It resumes its normal attachment to its segment 

 when the special branchial apparatus becomes abrogated, as in 

 the advanced batrachian, fig. 71, in which we saw the change of 

 position, as contrasted with the earlier piscine condition of the 

 larva, fig. 69 A. In the complex and ossified hyoidean arch of 



