.The Smooth Facial Muscles of Auura and Salamandrina. 321 



limits of the fenestra rostro-lateralis and is caused by the muscles for 

 openiug and closing the external naris compare Figs. 1, 2, 3, 4 and 6, 

 PI. XVII]. Within the muscle thickening lie the tubules of the glan- 

 dula nasalis externa, whose relation to the nasal muscles will be 

 considered later. The caudal part of the muscle thickening, together 

 with the gland, is covered by the facial portion of the maxillare. 



From the caudal end of the nasal muscle thickening, a slight 

 prominence, representing the turbinal of Wiedersheim (53) and 

 Born ^5), extends to the posterior wall of the nasal cavity. The 

 turbinal is supported by the planum terminale, which is slightly 

 bent into the nasal cavity (compare Figs. 3 and 5, PI. XVII). In 

 certain species (Plethodon erythronotus, Amblystoma tigriuum, Des- 

 mognathns fusca) this turbinal is strongly developed, and its anterior 

 end is supported by a small bone, the intranasale, which lies in the 

 caudal end of the fenestra rostro-lateralis (see Figs. 4 and (3, PI. XVII . 

 In Plethodon the intranasale has a simple tabular form and its caudal 

 margin lies in close contact with the edge of the planum terminale, 

 excepting where it its excavated to provide a passage for the ductus 

 uaso-lacrymalis. In Amblystoma occurs a similar, but much deeper, 

 excavation and the intranasale, which is large in this species, is thereby 

 divided into two arms, one of which lies above and medial, the 

 other below and lateral, from the ductus naso-lacrymalis. The dorsal 

 arm of the lacrymale lies in contact with the cartilago obliqua, the 

 ventral arm rests on the floor of the cartilaginous nasal capsule. 



The ductus naso-lacrymalis, which has been frequently men- 

 tioned above, discharges into the nasal cavity through the caudal 

 end of the fenestra rostro-lateralis. From its opening it bends around 

 the anterior margin of the planum terminale and extends caudal ward, 

 first between the planum terminale and the facial process of the 

 maxillare compare Fig. 3, PI. XVII), then through the prefrontale 

 (see Fig. 3, PI. XVII), on whose outer surface it emerges (Fig. 5, 

 PI. XVII) and divides into two branches which open on the inner 

 surface of the lower evelid. 



2. The Nasal Muscles. 



The muscle apparatus for closing and opening the external 

 uares of the salamanders consists in certain genera (Salamandrina, 

 Spelerpes, Diemyctylus) of two muscles only: a constrictor naris 

 and a dilatator naris. In other genera (Salamandra, Plethodon, 



