1G8 Inez Whipple Wilder. 



to tins environment; the attenuated body, reduced legs, and pro- 

 longed pointed snont are evidently adaptations to such a mode of life. 

 Moreover, it is terrestial in its egg-laying habits. O. P. Hay '88, 

 gives an interesting account of his observations of a large female 

 Amphiuma found guarding a mass of eggs at a considerable distance 

 from any water. Among other observations of this specimen, he calls 

 attention to the fact that the overlapping and interlocking lips afford 

 a very tight closure of the mouth against dirt while the animal is 

 burrowing, and that the gill slits are also capable of tight closure 

 against the entrance of foreign matter. 



Table Giving the Pkoportions of the Snouts of Various Urodeles. 



Triton alpestris 



Diemyctylus viridescens 



Dcsmognathus fusoa 



Cryptobranchus alleghenicTisis . 

 Aniphiuina tridactylum 



Ratio of length 



of snout to 

 width of head 

 from eye to eye. 



.82 

 .75 

 .87 

 .59 

 1.21 



ISTot only, however, is the mouth thus perfectly protected, but, 

 througli the action of the constrictor muscle of the naris, the delicate 

 nasal epithelium is also protected from the entrance of dirt. It will 

 be remembered, however, that the spiral fold which is dra^vn across 

 the nasal passage by the contraction of the constrictor naris muscle 

 is located not at tlie external orifice, but at the inner end of an intro- 

 ductory passage. Undoubtedly the persistence of this passage, which in 

 the salamandrids seems to be a larval organ disappearing with the 

 transition to the adult form, is correlated with the enormous elonga- 

 tion of the snout as an adaptation to burrowing. The relative pro- 

 portions of the heads of various urodeles are shown by the indices in 

 the accompanying table, Avhich serves Avell to emphasize the peculiarly 



