X.] THE COMMON FROG. 



153 



Outside the Frogs' own class, the differences may 

 be tabulated as follows : — 



The Frog differs from the entire class of FiSHES in 

 the following points : — 



1. It has a skeleton, the appendicular parts of 



which are divided into upper arm, fore-arm 

 and hand, and thigh, leg, and foot, respec- 

 tively. 



2. Its hyoid, when adult, has but one pair of 



cornua instead of several branchial arches. 



3. Its skull is bony, yet devoid of a basi-occipital 



bone. 



4. It has a pelvis formed of ilia, ischia, and pubes. 



5. Its coccygeal region is rudimentary. 



6. Its skin is devoid of scales. 



7. Its limb-muscles are numerous and complex. 



8. Its nostrils open posteriorly within the mouth. 



9. The ear is provided with Eustachian tubes. 



10. The tongue is large, fleshy, and free behind. 



11. The adult is devoid of gills. 



12. It has a larynx. 



13. It has lungs with a pulmonary circulation. 



14. It has no fin rays. 



15. It has no tail — in the adult. 



The Frog differs from all REPTILES in that— 



I. The skull has no basi-occipital bone, while it 

 at the same time has a large paraphenoid. 



2. There are two occipital condyles. 



3. Two of the tarsal bones are greatly elongated. 



