NASO-LABIAL GROOVE OF LUNGLESS SALAMANDERS. 3 



ousness being usually emphasized by the absence of pigment 

 along its course. It begins at the latero-ventral angle of the 

 external naris of which it is in a sense an exaggerated ventral 

 elongation. From this point it extends ventrally until it reaches 

 the edge of the lip, where it ends in a somewhat vaguely defined 

 horizontal groove (Fig. I, gi'l], which meets it at right angles. 

 This horizontal groove is parallel with the edge of the lip and 

 gradually disappears as it approaches the mid-line on the one 

 hand and the angle of the mouth on the other. 



In its connection with the external naris the naso-labial groove 

 shows a very definite relationship to certain structures which have 

 been worked out and described by Bruner ('96). This investi- 

 gator has shown that the Salauiandrida possess in connection with 

 the external naris a set of involuntary muscles for opening and 

 closing the orifice, the M. constrictor naris and M. dilatator naris 

 respectively. The constrictor is situated in the lateral wall of the 

 nasal cavity with its fibers partly encircling the orifice, so that ex- 

 ternally the visible effect of its contraction is to draw a crescentic 

 fold of skin (Fig. I, /") across the orifice from the outer toward 

 the inner border, the naris being thus partially or completely 

 closed according to the amount of contraction. By the contrac- 

 tion of the dilatator muscle, the fold is again -pulled back toward 

 the outer boundary of the naris. When the orifice is closed the 

 crescentic fold forms the floor of a slight depression which is com- 

 pletely encircled except at the latero-ventral angle, the point from 

 which the naso-labial groove leads. 



Associated with the external naris and with the naso-labial 

 groove are a number of well developed glands which I shall speak 

 of collectively as the naso-labial glands. Although these glands 

 show much individual variation, the location of their orifices is 

 practically constant for the species, the first two being specially 

 definite. The more dorsal of these (Fig. I , ///, ) is in the dorsal 

 angle of the naris, that is, at the end of the crescentic fold. The 

 second one (Fig. i, ;// 2 ) is on the ventral edge of the nasal orifice 

 at the point where the groove joins the naris and therefore upon 

 the mesial side of the groove. Arranged at approximately reg- 

 ular intervals along the mesial border of the groove are other 

 orifices, from six to twelve in number, and similar orifices occur 



