SKELETON AND LAETNX OE XEKOPTJS AND PIPA. 79 



of the dilator. If this suggestion be rejected the constrictor 

 muscle is not represented in Xenopus^. 



Compressor fflotfidis (PL 10. fig. 2, c). — Lying on the right and 

 left sides of the glottis and extending a short distance behind it is 

 a muscle which I take to represent the compressor glottidis f of 

 the frog, combined in all probability with the outer or posterior 

 compressor J. 



Henle calls it the " Compressor der Stimmlade " (19. p. 27, and 

 Taf. 2. fig. 5, p). In front it is attached, close to the median 

 line, to the upper surface of the basal plate of the hyobranchial 

 skeleton at a short distance behind its anterior border (PL 8. 

 fig. 1, 1/). The muscle passes directly backwards, excernal to the 

 arytenoid, and unites, behind the glottis, with its fellow of the 

 opposite side in a lijiea alba, some of the fibres being inserted 

 directly into the glottidean portion of the arytenoid cartilage 

 just at its junction with the massive posterior enlargement. A 

 broad sheet of fibrous tissue extends back from the hind end of 

 the muscles and linea alba to be inserted into the front edge of 

 roofing cartilage of the larynx. It is probably to be regarded as 

 an aponeurotic extension of the muscle itself. The indirect 

 connexion thus established between the muscle and the cricoid 

 cartilage is not without parallel, for Groppert states (16. p. 63) 

 that in the common frog some of the fibres of the external 



* Henle definitely states (19. p. 26) that the constrictor is absent in Pipa: 

 he makes no mention of it in Xenopus. The constrictor is absent in £om- 

 binator (Henle, 19- p. 24, and Wilder, 42- Taf. 21. figs. 46 and 47), a fact of 

 some importance considering how closely the hyobranchial and laryngeal 

 skeleton of this toad resembles that of Xenopus. Wilder has remarked its 

 presence in Alytes, and notes that it occupies an exceptionally ventral (cardiac) 

 position. Gronberg has recorded its occurrence in the male Pipa, but con- 

 cerning this see pp. 90 and 91. 



t Compressor, Henle, 19, p. 24, and Taf. i. fig. 42, jo'. 



Hoher, medianwarts liegender Constrictor, Ecker, H. fig. 14, Co.l. 

 Hyo-arytenoideus anterior, Ecker, 12. p. 315, and fig. 205, Co.l. 

 Sphincter anterior, Goppert, 16. p. 63. 

 Compressor laryngis. Wilder, 42- Taf. 20. fig. 31, cp. 

 X Compressor, Henle, 19. p. 24, and Taf. i. fig. 42, p". 

 Tiefer constrictor laryngis, Ecker, 11. fig. 14, Co.l'. 

 Hyo-arytenoideus posterior, Ecker, 12. p. 315, and iig. 205, Co.l'. 

 Sphincter posterior, Goppert, Ig. p. 63. 

 Sphincter dorsalis, Wilder, 42- Taf. 20. fig. 31, sf.d. 

 Duges does not discriminate between the two muscles, but applies the term 

 hyo-post-glottique to both, 10. p. 126, and PI. vii. (bis), fig. 47, no. 27. 



Saint- Ange calls them both constricteurs, SB- P- 421, and PI. 26. figs. 3', 4' 

 and 5', c and c'. 



