64 ILLINOIS BIOLOGICAL MONOGRAPHS [64 



branchs, Derotremes and Salamandroidia, 1 according as external gills 

 persist through life, as gill clefts remain permanently open or, in the latter, 

 as the animals undergo a complete metamorphosis, losing their external 

 gills and gill-clefts. 



Strauch (1870) divided the Urodeles into two sub-orders, the Salaman- 

 drida and the Ichthyoidea. The basis of his classification was the presence 

 or the absence of eyelids, the arrangement of the palatal teeth, and the 

 permanence of gills and gill clefts. The Salamandrida were subdivided 

 into two groups according to the arrangement of the palatal teeth. Those 

 Urodeles in which these teeth formed diverging rows upon the inner margin 

 of the palatine were grouped as the Mecodonta; while the Lechriodonta 

 included those animals in which the palatal teeth form converging rows 

 along the posterior margin of the palatine. The Mecodonta embrace six 

 genera of which Salamandra, Triton and Diemictylus are represented in 

 this paper; while of the thirteen genera included in Strauch's Lechriodonta, 

 I have studied Amblystoma, Plethodon and Spelerpes. 



The Ichthyoidea are divided into two groups, the Cryptobranchiata 

 and the Phanerobranchiata, according to the persistence of gill clefts only 

 or of both gills and gill clefts. Cryptobranchus, Menopoma and Amphiuma 

 belong to the former group; while Necturus, Proteus and Siren are included 

 in the latter. 



The nasal capsules would support a classification of the Urodeles 

 similar to that of Strauch. In the fore-going pages, I have included 

 Spelerpes, Plethodon and Amblystoma (part of the Lechriodonta of 

 Strauch) in a group descended from the more primitive Cryptobranchus; 

 while Salamandra, Triton and Diemictylus (the Mecodonta of Strauch) 

 are included in a group connected with the other group through some form 

 like Spelerpes. I have regarded Cryptobranchus as more primitive, and 

 Amphiuma as closely related to it, although not in the main line of descent. 

 Strauch has grouped Necturus and Proteus into the Phanerobranchiata 

 more distantly related to Cryptobranchus, while I have regarded Necturus 

 as a permanent larva of some Spelerpes-like animal. I have not studied 

 Proteus, but have placed Necturus in a separate group in keeping with 

 the later Perennibranchiate classification. 



Accordingly on the basis of the nasal capsules, I would adhere to the 

 classification of the Urodeles into three suborders, the Perennibranchi- 

 ata [Phanerobranchiata (Strauch)], the Derotrema [Cryptobranchiata 

 (Strauch)] and the Salamandroidia. The latter may be divided into two 

 groups, and, following Strauch, the terms Mecodonta and Lechriodonta 

 may be retained. 



1 In many text books, this is given as Salamandrina, but the group was called Salaman- 

 droidia by Fitzinger (1826) who in the same place describes a genus Salamandrina. Con- 

 fusion is therefore avoided by restricting the latter name to the genus while Salamandroidia 

 with its ordinal termination may be retained for the larger group. 



