420 



THE ZOOLOGIST. 



There are four gill or branchial arches that bear gills ; the 

 fifth branchial arch is stunted, bears no gills, but is furnished 

 with teeth. The first three branchial arches, counting from the 

 outside, are each composed of three bones — the hypo-, the 

 cerato-, and the epibranchials. In the fourth arch the hypo- 

 branchial is absent. The first branchial arch terminates in a 



Diagram showing Left Branchial Arches and Bones connected therewith. 



5th branchial arch, which 

 bears no gills, is dwarfed, 

 and called the lower pharyn- . 

 geal bone. 







4th branchial arch ; the hypo- 

 branchial is absent. 



3rd branchial arch. 





*0 



GlOSSQz 

 = ttYAL 



' 2nd branchial arch. 



1st branchial arch with a small 

 bone at the top "a" called 

 the upper epibranchial of 

 the first branchial arch. 



. . Bones bearing pharyngeal 

 teeth. 



The 1st, 2nd, 3rd, and 4th branchial arches all bear gills. 



small bone that helps in the attachment to the base of the skull, 

 it is called the upper epibranchial of the first branchial arch. 

 The second, third, and fourth arches terminate in the epi- 

 pharyngeal bones, which carry teeth. The outermost arch is 

 the longest, and they decrease in size inwardly; the hypo- 

 branchials are connected with the basibranchials — they and the 

 ceratobranchials form, as it were, the floor of the gullet; the 

 epibranchials curve upwards and meet together at the base of the 

 skull, forming, with the epipharyngeal bones, the upper part 

 and back of the gullet, the epipharyngeal bones being one above 

 the other, with that on the fourth branchial arch as the lowest. 

 The fifth arch, the lower pharyngeal bones, with its teeth, is on 

 the lower part of the floor of the gullet, and in advance of the 

 oesophagus. The above is approximately a description of the 



