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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 M. maculatus and M. 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- 

 tologists, one may conclude, that though one species or variety of 

 Menobranchus is found in the same system of waters as the Meno- 

 poma, the Menopoma has not hitherto been observed in the same 

 lakes, or indeed in the same district of country, where one variety or 

 species, viz. the Menobranchus maculatus, is alone found, and where 

 it is abundant. 



But an experienced American naturalist, Dr. Baird, has ob- 

 served, that " the non-discovery of the adult is no argument against 

 its existence. I had caught hundreds of the very remarkable larva 

 of Pseudotriton Salmoneus near Carlisle, before I found an adult." 

 (Journ. Acad. N. Sci. Philad. 1849, 292.) 



Dr. Holbrook observes, that " the Menobranchus maculatus is 

 seldom taken except in the months of April and May, which 

 is their spawning season. Their eggs are about the size of peas, 

 and as many as one hundred and fifty have been counted in a single 

 female." 



This would lead one to believe that they are adult animals ; but 

 eggs have been equally found in the Axolotl of Mexico, which is re- 

 garded by most naturalists as a larva. 



3. It is to be observed, that though the Proteus of the Lakes 

 (Necturus) has a more distinct and separate opercular flap, united by 

 a distinct fold under the throat, than either the Proteus of Carniola 

 or the Siren, and in this respect more nearly resembles the Axolotl 

 of Mexico and the larva of Tritons — yet, that, like the Proteus an- 

 guinus and the Siren, it has only two slits on each side of the neck, 

 with a single free ray between them, the anterior and posterior car- 

 tilaginous ray being united to the skin, as in those genera ; while 

 the Axolotl and the larva of Tritons have the gill flat, quite free from 

 the gill-rays, and there are three slits between the gill-rays as well 

 as the larger anterior one, making four slits on each side, and the 

 inner edge of the rays being toothed as in fishes. 



From these considerations I am inclined for the present to consider 

 the Proteus of the Lakes as a distinct kind of Batrachian, which 

 is arrested in its development and never reaches the perfect state. 



The skull is much more developed than in the other genera of 

 Meantia, and in its outline and disposition of its teeth it resembles 

 that of the genus Protonopsis as figured by Cuvier (Oss. Foss. ii. 



