THE RANK OF NECTURUS AMONG THE TAILED AMPHI- 

 BIANS AS INDICATED BY THE DISTRIBUTION 

 OF ITS CRANIAL NERVES. 



BY H. W. NORRIS. 



That "the Proteidae constitute the most primitive of the Urodeles" 

 (Holmes, 1906) is generally accepted as an established fact. But here 

 and there one tinds dissenting opinions from this particular view. 

 Kingsbury (1905) has given some very instructive and suggestive com- 

 parisons, chiefly of skeletal features, between Necturus and typical Uro- 

 dela showing that Necturus and the larval stages of Spelerpes have so 

 many characters in common that the similarities must stand for some 

 degree of close relationship. His conclusions are expressed as follows: 

 "I believe that the characters in the cranium of Necturus that are dis- 

 cussed here are those that are also characteristic of the larvae of many 

 tailed Amphibia, especially of certain forms (family Plethodontidae), 

 and that the acceptance of Necturus as a permanent larva best ex- 

 plains at present these features." Moodie (1908a) in his studies on the 

 lateral line system of the extinct Amphibia cites Kingsbury as evidence 

 in these words : "Kingsbury has expressed it as his opinion that Necturus 

 is a primitive form." It is difficult to reconcile this statement Avith the 

 above ((notation from Kingsbury. ^loodie draws his own conclusions as to 

 the zoological position of Necturus from the arrangement of the lateral 

 line organs on the tail. According to him Necturus is the only modern 

 amphibian in which the median and dorsal lateral lines of the trunk 

 extend to the extreme tip of the tail, in this respect resembling certain 

 of the Stegocephali. In view of our meager knowledge of the distribu- 

 tion of the lateral line organs on the trunk of modern amphibians the 

 writer does not feel justified in criticising this opinion of Moodie. It 

 may be noted here incidentally that Moodie (1908b) considers the tailed 

 amphibians as the degenerate descendants of the Branchiosauria. 



Druner (1904) cites Boas (to whose paper the writer has not had 

 aj3cess) to this effect: "dass Siren, Menobranchus (Necturus) und 

 Proteus Larvenformen seien, welche von Caducibranchiaten Urodelen 

 abstammen, die einst eiiie Umwandlungen besassen and erst spater zum 



