PEREXNIBRANCHIATA. II 



il and Bibron ; Pseudophydiens,De Blainville ; Sirenideae, 

 Tenney; Ichtyoides, Latreille. 



Branchiae persistent; prefrontal, nasal and maxillary 

 bones wanting; praemaxillae not anchylosed together; 

 pterygoid absent, or united with the palatines; verte- 

 brae amphicoelous ; carpus and tarsus cartilaginous, the 

 latter sometimes absent ; eyes without lids, in some cases 

 surrounded by circular ring resembling a lid. 



Pelvic arch and limbs wanting . . Trachystoma. 



Pelvic arch and limbs present Proteida. 



TRACHYSTOMA. Muller 



Skull elongated; parasphenoid edentulous; vomer 

 with teeth; praemaxillae and dentaries armed with 

 horny plates ; pterygoidea wanting ; occipital condyles 

 sessile; first two ceratohyals distinct; branchiae, bran- 

 chial apertures, and four pairs of arches persistent; 

 eyes surrounded by a circular lid ; carpus cartilaginous ; 

 pectoral arch and limbs developed, pelvic wanting ; ante- 

 rior digits three or four. 



