SKELETON AND LAETNX OP XENOPUS AND PIPA. 85 



slender than in the female, but exhibits, even in a more marked 

 degree, the same diminution in width in that part of its length 

 which underlies th.e anterior end of tbe larynx. It runs dorsally 

 to the petrohyoideus as in the female, but is separated from the 

 cartilaginous floor of the larynx by the intruded sheet of the 

 dilator. 



The petrohyoideus (PI. 10. fig. 3,^) is also more feebly developed 

 than in the female. Only the anterior fibres reach the median 

 line, so that a triangular sj)ace of bare cartilage is left between 

 the hinder parts o£ the expanded laryngeal extremities of the 

 muscle. The radiation of the fibres is much more uniform and 

 regular than in the female. The compressor glotticUs (PI. 10. 

 fig. 4, c) does not differ materially from that of the female. 

 Many of the fibres are distinctly attached to the arytenoid car- 

 tilage posteriorly, and the connexion of the muscle with the 

 fascia-sheet covering the dorsal surface of the arytenoid plate 

 (PI. 8. fig. 6, ar.') is comparatively unimportant. Owing to the 

 feebleness of the anterior dilator, the anterior and posterior 

 bellies of the compressor are less distinct than in the female, and, 

 when the muscle is isolated and examined under the microscope, 

 muscle-fibres can be seen passing from one belly to the other. 

 In the female, the intervening part is wholly tendinous. 



Laryngeal Mttscles oe JPipa americana. 



The first description of tbe hyobranchial and laryngeal 

 muscles of Pipa we owe to Mayer (25), who includes them in his 

 chapter on the general muscular anatomy of the female. Meckel 

 (28) paid some attention to the subject, as also did Henle (19). 

 Henle's description applies to the female sex *, and is well illus- 

 trated. More recently, Grronberg (18. pp. 637 and 638) has 

 resumed the study of the subject, but his remarks refer ex- 

 clusively to the intrinsic muscles of the male larynx. His figures 

 {Taf. 38. figs. 18-20) are, however, most valuable, being the only 

 illustrations extant of the laryngeal muscles of that sex. 



Female. 

 The muscles in relation with the larynx in the female Pipa 

 resemble in the main those of Xenopus. The same arguments, 

 therefore, which have previously been adduced for determining 



* Not male, as stated by Gronberg (18. p. 637). 



