CLASSIFICATIONS OF THE AMPHIBIA. 375 



peculiar modification of gills, by which the air from the wa- 

 ter is imparted to the blood in the branchial arteries, I would 

 then erase the provisional order Imperfectibranchia, and thus 

 re-arrange the last sub-class : — 



Sub-class II.— DIP LOPNEUMEN A. 



Order III. — Manentibranchia. 



Tribe 1. Internibranchia. Gills plain, internal. 



Family. Menopomatidce. 



Tribe 2. Externibranchia. Gills tufted or ramified, external. 



Families. Sirenidce. Proteidce. 



But, on the contrary, should future experiments prove that 

 the branchial apparatus in the Menopomatidce is decidedly 

 imperfect, and that it has no share whatever in aquatic respi- 

 ration, then it will become necessary to modify my classifi- 

 cation after this manner : — ■ 



Class IV.— AMPHIBIA. 



Sub-class I.-MONOPNEUMENA. 



Order I. — Abranchia. Branchial apparatus none. 



Family. Cceciliadte. 



Order II. — Caducibranchia. Branchial apparatus decaying. 



Families. Ranidce. Dactylethridce. Astrodactylidce. Salamandridce. 



Order III. — Imperfectibranchia. Branchial apparatus imperfect. 



Family. Menopomatidce. 



Sub-class II.— DIPLOPNEUMEN A. 



Order IV. — Manentibranchia. Branchial apparatus remaining. 

 Families. Sirenidce. Proteidce. 



And lastly, if the Menopomatidce be hereafter ascertained 

 to undergo a metamorphosis ; and if the very young animals 

 really possess the external branchiae, but which are very early 

 deciduous ; which Cuvier thought likely, for he says,— " pro- 

 bablement qu'ils les perdent d' aussi bonne heure que notre 

 salamandre terrestre;" 1 — and the branchial arcs, lids, and 

 apertures remain permanent throughout life ; I will, in such 

 case, propose the following arrangement : — 



Class IV.— AMPHIBIA. 

 Sub-class I.—MONOPNEUMENA. 



Vide 'Regne Animal,' tome ii. p. 117, edit. 2. 



