88 ' ME. W. G. EIDEWOOD ON" THE HTOBEANCHIAIi 



quadruple nature of the hyoglossal muscle posteriorly. He also 

 states (p. 77) with. Mayer (25, p. 537) that the external hyoglossus 

 arises from the thyrohyal or columella. Careful dissection, how- 

 ever, shows that the origin is internal to the cartilage which is 

 to he regarded as the epiphysis of the thyrohyal. 



The petroTiyoideus (PI. 10. fig. 6, p) arises from the membranous 

 ventral wall of the larynx, close to the median line, at about one- 

 third of the length from the posterior end. It extends outwards 

 and backwards, coils round the external edge of the great wing 

 of the hyobranchial skeleton, and, passing forwards and upwards, 

 is attached to the dorso-exterual crest of the auditory capsule, 

 close beside the inner end of the columella auris. It runs ventral 

 to the hyoglossus and the geniohyoideus externus, but dorsal to 

 the obliquus internus. It is a very long and meandering muscle, 

 and is of uniform width all along, except at its laryngeal extremity. 

 It is relatively smaller than in the female Xenopus. 



Geniohyoideus (Mayer, 25. p. 538; Henle, 19. Taf. 2. figs. 22 

 and 23, 3). — Henle (p. 26) has already noted that the inner divi- 

 sion of the geniohyoideus, attached to the laryngeal skeleton in 

 Xenopus, is absent in Pipa. The external division is a long, 

 slender muscle, of even diameter, extending from the symphysial 

 region of the mandible to the postero-external region of the 

 ventral surface of the great hyobranchial ala. The position of its 

 insertion is shown at ffe. in fig. 1, PI. 9. The recognition of 

 this muscle in the embryo is a matter of no great difficulty, and 

 as soon as the wing of the hyobranchial skeleton is clearly differ- 

 entiated from the neighbouring parts, the insertion of the muscle 

 is seen to be related to it exactly as in the adult (see Pi. 11. fig. 8, 

 ffe.). Seeing that the wing is purely a derivative of the hypo- 

 branchial plate of the larval skeleton, it would be more satis- 

 factory to substitute for geniohyoideus the word geniohypo- 

 branchialis, the name by which Schulze (38) designates this 

 muscle ^Ti his treatise on the development of PeZoSa^es. It is 

 worthy of remark that, while in Pipa the geniohyoideus externus 

 is attached to the ala near its posterior edge, the position of the 

 insertion of this muscle in X.enopus lies in front of the line 

 joining the anterior extremities of the thyrohyals (see ge. PI. 8. 

 fig. 1 and PL 9. fig. 1). 



Ohliquus internus (PI. 10. fig. 5, o.i.). — In the larynx of the 

 young but sexually mature female depicted in fig. 5, PL 10, the 

 laryngeal division of the internal oblique muscle is of consider- 



