220 ME. G. P. MUDGE OX THE MYOLOGY 



Stage 5. 



In this stage the ventral fascia of the muscle is still tendinous, and to the same 

 extent as that of the lower stages, but the thickened tract of Stage 4 has become 

 slightly more pronounced, and has partially separated from the tendinous fascia, so 

 that to a certain degree it is an individual tendon. There is also a very marked 

 tendency for the ceratoglossus inferior posticus to extend back to the posterior extremity 

 of the hypobranchial, and the retrogression of the inner portion of the ceratoglossus 

 inferior anticus is becoming very pronounced, the muscles of some Parrots having 

 reached almost complete retrogression (=111) in respect of this portion. 



In Psittacus erithacus the muscle is typically represented at this stage. It is figured 

 on PL XXVIII. fig. 29, and in its general features resembles that in Chrysotis 

 OL-hrocei)lialus, from which it diff'ers, in addition to the characters of the teudon, in 

 that the ventral fascia is thicker (which cannot be well represented in a figure) and the 

 inner portion of the ceratoglossus inferior anticus [cg.i.a}.') sends back a small twig on 

 to the head of the hypobranchial (HB.). The ceratoglossus inferior anticus accessorius 

 (cc/.i^.) is of the usual type, and is not like that in Chrysotis oclirocephalus. 



The muscle in Coracopsis vasa (PI. XXVIII. fig. 31) is similar to that in Psittacus, 

 but the inner portion {cg.i.a^.) of the ceratoglossus inferior anticus is very strongly 

 developed, and anteriorly, like that in^r«. macao, it is covered with a tendinous fascia ; 

 it does not, like that iu Psittacus, send back a small twig on to the hypobranchial. 

 The ceratoglossus inferior posticus {cg.i.]).) extends along the hypobranchial for its 

 anterior half only. 



In Pcdceornis torquata (PL XXVIII. fig. 32) and Psephotus xanthorrhoiis the cerato- 

 glossus inferior posticus reaches to the posterior limit of the hypobranchial ; in the 

 latter Parrot the inner portion of the ceratoglossus inferior anticus has quite disappeared 

 ( = stage III) ; but in Palceornis it has only attained to between this and II. 



In Conurus holochlorus, C. jendaya (PL XXVIII. fig. 36), and C. cactorum 

 (PL XXVIII. fig. 30) the ceratoglossus inferior posticus extends nearly the whole 

 length of the hypobranchial. In the last of these three Parrots the inner portion of 

 the ceratoglossus inferior anticus {cg.i.a}.) is strongly developed, that of either side, 

 turning inwards, becomes slightly separated from the outer part and meets its fellow 

 m the middle line ; in the first-named Parrot it has retrogressed almost to stage II, and 

 iu the second almost to stage III. 



In iJeroptyus accipitrinus the ceratoglossus inferior posticus extends a little more 

 than the anterior two-thirds along the hypobranchial, and the inner portion of the 

 ceratoglossus inferior anticus has retrogressed to stage II. The ceratoglossus inferior 

 anticus accessorius resembles that in Cacatua galerita (PL XXVIII. fig. 25) in its 

 mode of attachment to the uro-hypobranchial tendon — i. e., it is attached to the ventral 

 surface, instead of to its anterior margin as in the majority of Parrots. 



In Eclectus ijectoralis (PL XXIX. fig. 49) the ceratoglossus inferior posticus {cg.i.p.) 



