348 Henry L. Bruner 



whose facial portions they enter, as already stated, near the dorsal 

 end. On account of this relation the processus praenasales in- 

 feriores resist both the elevation of the median parts of the 

 intermaxillaria and the increase of the angle of divergence 

 of their facial portions. When, therefore, the muscles which 

 produce elevation of the intermaxillaria cease to contract, the pro- 

 cessus praenasales inferiores, aided by the elasticity of other parts, 

 entirely reverse the movements which occur during the closing of 

 the nares. The palatine portions of the intermaxillaria are ac- 

 cordingly depressed in the median line, their facial portions become 

 less divergent and carry the processus praenasales superiores medial- 

 ward. At the same time the cartilago alaris on each side moves in 

 a lateral direction and opens the naris. It is through the operation 

 of such elastic forces, that the external nares of a dead frog are 

 opened after they have been closed by the elevation of the rostrum. 

 An active opening of the external nares of ßana may, 

 however, also be occasionally observed in the living ani- 

 mal, particularly in strong inspiration. It is to be accounted 

 for, as already shown by Gaupp (20), by the contraction of the 

 geniohyoideus muscle, whose medial portion arises from the partes 

 mentales of the dentalia above the submentalis. Contraction of 

 the geniohyoideus depresses the partes mentales, and with 

 them also the median parts of the intermaxillaria, which 

 are closely united, by means of their incurved dentary 

 portions and by the upper lip, with the partes mentales of 

 the lower jaw. 



3. Homology of the Nasal Muscles of Eana. 



In determining the homology of the nasal muscles which I 

 have described in Rana fusca it is necessary to take into considera- 

 tion not only the muscles which occur in the salamanders but also 

 the results attained by earlier workers who have described muscles 

 for opening and closing the external naris in Anura. It has 

 indeed been shown by Gaupp (21) that special muscles for the 

 immediate opening and closing of the external nares are wanting in 

 liana. The same author has also affirmed the entire absence of 

 muscles in those regions where the muscles of the earlier writers 

 should be located. It must not be forgotten, however, that the 

 muscles of the earlier authors were supposedly of the striped variety, 



