90 ME. W. a. EIDEWOOD ON THE HTOBEA.KCHIAL 



forced to conclude that the muscle also is unique. He does not 

 suggest any name for it. The third muscle overlaps the other 

 two on the external or lateral surface of the larynx, and its tendon 

 (18. fig. 20, S 2) unites antero-ventrally to the glottis with its 

 fellow of the opposite side. Prom these relations he considers 

 it to represent the " hoher, lateralwarts liegender Constrictor des 

 Larynx" of Ecker (11. p. 31, fig. 14, c.a.l.) (called in the English 

 edition the " Constrictor aditus laryngis," 12. p. 314, fig. 205^ 

 c.a.l.). 



On comparing Grronberg's figures of the male with mine of the 

 female, it will, I think, be evident at a glance that the dorsal 

 muscle, the tendon of which he marks SI, is that which I have 

 called the dilator anterior (PI. 10. fig. 5, d.a.). The tendon in 

 both cases is inserted into the edge of the arytenoid cartilage at 

 the side of the glottis, and it is quite possible to conceive that 

 the muscle has assumed a more antero-posterior direction in the 

 male, in consequence of the glottis opening directly forwards, 

 towards the aperture of the mouth, instead of upwards as in the 

 female. The other two, ;S' 2 and S 3,1 take to correspond with 

 my dilator laryngis. Although in both sexes of Xenopus the 

 insertion of the dilator lies entirely behind that of the dilator 

 anterior (PI. 10. figs. 2 and 4), yet in the female of Pipa the 

 attachment of the tendon of the dilator to the promontory of 

 the arytenoid is situated farther forward than the insertion of 

 the anterior dilator into the side-wall of the glottis (PI. 10. fig. 5), 

 Assuming, as I think we are justified in doing, that the promon- 

 tory of the female arytenoid (PL 9. fig. 2, d) is equivalent to the 

 similar promontory of the male which Grronberg marks a in his 

 figures 10, 11, 13, and 14, it is but logical to regard his ventral 

 muscle, S 3, and my dilator laryngis as identical. This leaves 

 only his muscle 82 unaccounted for. 



I have not been able to recognize in the female Pipa any third 

 dilator, nor any union of tendons anterior to the glottis ; but in 

 both sexes of Xeiiopus there is an imperfectly difi'erentlated slip 

 of the dilator (PI. 10. figs. 2 and 4, d'), the tendon of which is 

 elongated and inserted into the massive part of the arytenoid. 

 It is true that in Xenopus the insertion of the slip is far behind 

 that of the dilator anterior and the glottis, but an examination 

 of fig. 5, PI. 10, will show that a similar slip differentiated from 

 the more dorsal part of the dilator, on the rotation of the glottis 

 forwards, would come to occupy the position of Grronberg's 82, 



