XIII 



PHYLUM CHORDATA 



295 



an internal or ventral surface, an anterior or pre-axial border 

 which terminates in the first digit and a posterior or post-axial 

 border which terminates in the last digit. The eyes are small 



a 



s 



* ? 

 1 I 



and have no eyelids, there is no tympanic membrane, and the 

 mouth is wide and bordered by thick lips. On each side of the 

 neck are two gill-slits (br. cl. 1, br. d. 2) leading into the pharynx, 

 the first between the first and second branchial arches, the other 



T 2 



