1 68 WILLIAM A. HILTON. 



family Plethodontidse, especially in the character of the very 

 long first cerato-branchial, Fig. 3. 



By a comparison of the hyo-branchial apparatus of larval 

 Typhlotriton with the same parts in the larvse of the Pletho- 

 dontidse, a striking resemblance may be noticed, especially in the 

 fact that in Typhlotriton as in Spelerpcs for instance, Fig. 4, there 

 are only three branchial bars, while the general proportions of all 

 the parts are about the same, as the figures show. 



FIG. 2. Hyo-branchial apparatus of nearly full grown larva of Desmogna- 

 tlms fusca from above, showing four branchial bars. X 6. 



If the hyoid apparatus of Typhlotriton larva be compared with 

 that of Typhlomolgc, another cave form, but one that has external 

 gills, a very striking resemblance is found between the two, Fig. 

 5. Emerson 1 who describes the hyo-branchial apparatus of this 

 form, suggests that it shows in many ways a marked resemblance 

 to a Spelerpes larva and that it differs widely from the members 

 of the family Proteidse in which it has been placed. 



May not this then be a larva, possibly a permanent larva as sug- 

 gested by Kingsbury- for Necturus? At any rate judging from 

 the hyoid apparatus alone there seems to be a rather close 

 relationship between the two forms Typhlomolge and Typhlo- 

 triton. 



In comparing the hyoid apparatus of Typhlotriton with that of 

 larval Spclerpcs, it may be noted that in all essential respects the 

 two structures are alike. There is a slight difference in the 

 proportions of parts, and the tip of the " Copulastiel " of Gaup, 

 has three parts in Typhlotriton while it only has one in Spelerpes. 

 The similar one of Typhlomolge we find divided into two. 



1 Emerson. 2d, Ellen T., " General Anatomy of Typhlomolge rathbuni," 

 Proc. Bost. Soc. Nat. Hist., Vol. 32. No. 3. 



2 Kingsbury, B. F.. "The Rank of Necturus among Tailed Bacteria," 

 BIOL. BULL., Vol. VIII., 1905. 



