Dr. J. E, Gray on the genus Necturus or Meiiobranchus. 315 



and the subcentral foramen. In the poisonous Snakes the duct of 

 the poison occupies this cavity ; and the similarity of the form and 

 structure h'ads to the idea that it may be used for the same purpose 

 in the Vrotens of the Lakes. 



The chief difference between the teeth of the Proteus of the Lakes 

 and the fangs of Serpents, is, that in the former the upper aperture 

 of the cavity is nearer to the centre of the tooth, some distance 

 from the apex, while in the fang of the Serpent it is generally near 

 to the tip. 



I know of no other instance of a Batrachian having this structure 

 of its teeth, nor do I know any instance, except in the Mexican 

 Lizard, called Helodenna horridum, in which all the teeth are uni- 

 formly furnished with a basal cavity and foramen ; and this Lizard 

 is said to be noxious, but the fact has not been distinctly proved. 



2. When Dr. Barton, in his paper on the Siren, first described 

 the Hell-bender (FrotonojMis horridu), he considered the Proteus of 

 the Lakes as the young state of the latter species. 



The skull bears more affinity to the skull of that animal than to 

 that of any other Batrachian, and the difference between them is 

 just such as one might ex})ect between the larva and adult of other 

 similar animals ; and it will be observed that the Proteus of the 

 Lakes is only known in its larva-like state, and Protonopsis, as far 

 as I know, only in its adult form. 



The first great, and indeed almost insurmountable, argument 

 against regarding the Proteus of the Lakes and the Hell-bender as 

 two states of the same species, is the geographical distribution of the 

 animals as given by the American herpetologist. 



Thus Holbrook, for example, states, "TheMenopoma AUeghanien- 

 sis (Hell-bender) is found iu the Alleghany river and its tributaries, 

 and doubtless inhabits many of the branches of the Ohio and Missis- 

 sippi rivers ; " and 3/. fisca, " the waters of the mountainous regions 

 of North CaroUna and Georgia ; " while the Proteus of the Lakes 

 {Menobranchus maculatiis) has as yet been found only in Lake 

 Champlain and Lake Erie and their tributary streams. 



It is true that a second species of the genus, Menobranchus lateralis, 

 according to Dr. Holbrook, " has a wide range, it being fomid in many 

 of the rivers and streams that open into the Mississippi on its eastern 

 side ; but I am not aware of its existence west of that river. Say 

 found it as far north as Pittsburg in Pennsylvania, and Troost as far 

 south as Cumberland river in Tennessee :" and further, " the Meno- 

 branchus lateralis was first described by Say from a specimen taken 

 by a hook in the Alleghany river." He proceeds: "At first I was 

 disposed to believe that the 3/. maculatus and 31. lateralis were one 

 and the same animal, but I am now convinced that the latter is at 

 least a well-marked variety, if not a distinct species ; it is more slender 

 in proportion, its colours and markings different ; it is found only in 

 the western waters that run into the Mississippi, while the former 

 inhabits the rivers and streams that flow into the northern lakes, and 

 all the tributaries of the St. Lawrence river." 



From these remarks on the observations of other American herpe- 



