The Smooth Facial Muscles of Anura and Salamandrina. 341 



opening, terminates above, however, in connective tissue, which 

 occupies the dorsal part of the plica obliqua and inserts as a com- 

 pact bundle on the medial margin of the nasal opening. The muscle 

 is also surrounded by connective tissue which is continuous in a 

 caudal direction with the fibrous investment of the glandula nasalis 

 externa. This muscle, which I shall in advance assume to be 

 homologous with the dilatator naris of the salamander, is limited to 

 the ventral (caudal) half of the plica obliqua; it forms, however, with 

 the connective tissue of the upper part of the plica a functional unit, 

 which extends from the ventral (caudal), to the dorsal (rostral), end 

 of the cartilago obliqua (see Fig. 8, PI. XVII and Figs. 11 to 14, 

 PI. XVIII). The size and condition of this muscle varies somewhat 

 in different individuals. In older specimens of Rana fusca I have 

 found it to consist of isolated bundles of muscle fibers separated by 

 a relatively large amount of connective tissue. 



A second muscle, also smooth, lies behind the nasal opening 

 and the vestibule of the cavum superius. Before we undertake its 

 description, however, we must examine, somewhat carefully, the 

 anatomy of the roof of the nasal cavity adjoining the nasal opening. 

 As already stated, the medial margin of this opening is supported 

 by the rostral (dorsal) end of the cartilago obliqua (roof of the nasal 

 capsule). In the anterior part of this margin the cartilage approaches 

 close to the epithelium, but farther caudalward the cartilage retreats 

 from the opening, which is accordingly bounded here by soft tissue 

 only. In this soft margin is inserted the median portion of a 

 muscle, whose lateral portion inserts partly in the plica obliqua and 

 partly in the caudal wall of the vestibule of the cavum superius. 

 This muscle (see Fig. 8, PI. XVII, and Figs. 11 to 14, PI. XVIII) 

 lies outside of the cartilago obliqua and arises, in Rana fusca, 

 near the caudal margin of that cartilage and from the connective 

 tissue enveloping the glandula nasalis externa. The medial (dorsal) 

 part of the muscle is composed of compact bundles, which lie dorsal 

 from the nasal gland and arise from the dorsal (medial) portion of 

 the cartilago obliqua and the connective tissue which invests it. 

 These bundles are inserted in the soft portion of the median margin 

 of the nasal opening, and near by in the lateral portion of the plica 

 obliqua. The lateral (ventral) part of the muscle consists of some- 

 what separated bundles, which arise partly lateral from the glandula 

 nasalis externa and in })art from the connective tissue which lies 

 between the tubules of the gland; these bundles insert beneath the 



