240 ME. G. p. MUDGE ON THE MYOLOGY 



are distinguished in llic comi^ete separation of the two muscles in the stage now under 

 consideration. 



In Falworyiis torquata (PI. XXVI. fig. 7, th.g.) and Tanygnathus mulleri the muscle 

 arises from the inner surface of tiie entoglossum a little anterior to its posterior extremity, 

 and is inserted at tlie dorso-lateral surface of the thyroid ; it is narrow at its origin, 

 but very wide at its insertion. In Loriculiis gak/ulus (PI. XXVII. fig. 23) the muscle 

 is like that in Pald'ornis, but it arises from the posterior extremity of tlie entoglossum. 

 In Ara araranna tlie muscle is similar to that in Falawnis, but it is much attenuated. 

 In Ara macao (PI. XXVII. fig. 20) the muscle is well developed and arises from the 

 tendon of the hypoglossus obliquus just posterior to the origin of the latter from the 

 posterior extremity of the entoglossum ; its insertion is for the most part to that 

 portion of the membrane (m.) of the tongue that covers the thyroid on either side of 

 the glottis, and also to a small extent to the upper margin of the dorso-lateral surface 

 of the thyroid. In Pionopsittacus inleatus the muscle resembles that in Falceornis, 

 but its origin is tendinous. In Psittinus incertus the muscle appears to be double. 

 It consists of two perfectly distinct parts closely bound together by connective 

 tissue, which arise from the posterior extremity of the entoglossum, and become 

 inserted, one to the dorso-lateral surface, and the other to the ventro-lateral surface 

 of the thyroid. The former of these parts is undoubtedly a thyroglossus, and the 

 latter, in virtue of its insertion, is a thyrohyoideus, but a thyroglossus on account of 

 its origin : probably it is a thyrohyoideus that has acquired a new origin, and we 

 can understand how, if old associations tend to be preserved and the thyroglossus arose 

 by Method C, that it was carried forward to the entoglossum. 



In Ptistes erythropterus (PL XXVI. fig. 6) the condition that is foreshadowed in 

 Cacatua triton {ante, p. 237) has attained its full development, for the rudimentary 

 bifid nature of the free extremity of the muscle there indicated has in Ptistes developed 

 into a well-pronounced fork of two prongs, the larger of which has formed a tendinous 

 origin at the inner surface of the posterior lateral process of the entoglossal of the 

 same side of the tongue, while the smaller one crosses the middle line and reaches its 

 origin at the same position on the entoglossal of the other side. 



Stage 4. 



In this stage the muscle is characterized by having a double origin, i. e. one from 

 the entoglossum and another, more or less strongly developed, from the parahyal 

 process. 



In iJeroj^tyus accApitrinus that part of the muscle which arises from the entoglossum 

 is very much the stronger of the two, and in fact constitutes almost the whole of the 

 origin; the part arising from the parahyal process consists of only a few fibres. The 

 insertion is the usual one. In Conurus ItolocJilorus the two origins are more nearly 

 equal, that at the entoglossum being slightly larger than the other; the part arising 



