THE AMPHIBIA. 173 



pearing only in advanced age ; no eyelids ; vertebra 

 amphiccelous; carpus and tarsus cartilaginous. 



1. Proteldea. 

 h. 'So branchiae or branchial clefts in the adult; eyelids 

 present; carpus and tarsus more or less ossified; 

 vortebras commonly opisthocoelous. 



2. Salamnnrlridea. 

 B. Limbs absent, or all four present. Three large pec- 

 toral osseous plates and an armour of small scutes on 

 the ventral surface of the body : vertebras amphi- 

 ccelous ; walls of the teeth more or less folded. 

 II. Labyrinlhodonta. 



B. Tail obsolete in the adult. 



A. Limbs absent ; numerous minute dermal scutes im- 



bedded in the integument of tlie serpentiform body. 



III. Gymnophiona. 



B. All four limbs present, and the proximal elements of 



the tarsus much elongated ; the body short, and the 

 integument devoid of small scutes, though dermal 

 osseous plates are sometimes developed in it. 



IV. Batrachia or Anura. 



The integument in most Amphibia is soft and moist, as in 

 the Frog, where numerous glands open upon its surface. 

 The Gynmophiona are exceptional, among existing Amphibia, 

 in possessing small, roitnded, flexible scales, like the cycloid 

 scales of fishes, imbedded within the wrinkled integument. 



In certain Batrachia [Ceratophnjs dorsata. Ephippifer 

 aurantiacus), fiat dermal bony plates are developed in the 

 dorsal integument, and become united with some of the 

 subjacent vertebra?. Many of the extinct Labyrinthodonta, 

 and probably the whole of the members of that group, pos- 

 sessed an exoskeleton which appears to have been confined 

 to the ventral surface of the body. Under the anterior part 

 of the thorax there is a sort of plastron composed of one 

 median and two lateral plates. The median plate is rhom- 

 boidal. The lateral ones are somewhat triangular, and unite 

 with the anterolateral margins of the median plate by one 

 side, sending a process upwards and backwards from their 

 outer angles. The outer surfaces of all these plates exhibit 

 a sculpture, which radiates from the centre of the median 

 plate and from the outer angles of the lateral plates. These 



