2U mi. G. p. MUDGE OX THE MYOLOGY 



to the cdgo of the glottis, into tlie anterior two-thirds of whicli it is inserted. Tt has 

 advanced very far in its retrogression, and consists only of the fascia with a few 

 muscular fibres ; I shall speak of it as the tliyrohijoideiis accessorms transversalis 

 (PI. XXIX. fig. 46, th.h.a.f.). 



In all the species of 6'oM?(r»6', C/ir//sotis, Ara, Dcrojdi/tis, and Cijanolyxciis the muscle is 

 narrow at its origin and widens at its insertion. In Conurus jendajja (PI. XXVI. tig. 9) 

 and C. holovhiorus the muscle is merged with the thyroglossus at its posterior end i ; in 

 Cyanolyseus jjatagonicus and Pyrrhura leucotis (PI. XXVII. fig. 19) the confluence is 

 greater, aud in Conurus cactorum the two muscles are represented by a single one with 

 a double origin, which is very similar to that in Brotogerys (text-lig. 9, p. 2oS, th.h., 

 th.g.). In Chrysotis, Deroptyus, and Ara the muscle, though lying in contact with the 

 thyroglossus in its posterior region, is not confluent with it at any part. In Psittacus 

 (PL XXVII. fig. 15) and Coracopsis (Plate XXVII. fig. 17) the thyrohyoideus is 

 hidden by the thyroglossus, which overlies it somewhat dorso-laterally, and in the latter 

 bird it is narrowed at its origin. In Psittacula and Pezoponts(P\. XXVI. fig. 8) there 

 is a like condition, but the thyroglossus lies wholly dorsally to the thyrohyoideus. In 

 Pahvornis (PI. XXVI. fig. 7) the thyrohyoideus is very thin and narrow ; it is slightly 

 stouter in Tanygnathus ; and in Loricuhis galguhis (PI. XXVII. tig. 23), in addition, 

 it narrows very considerably at its insertion. In Pollorlrynchus tlie relation of the 

 muscle to the thyroglossus is similar to that in Platycercus (PL XXVI. fig. 11), but it 

 is confluent with that at its origin aud insertion, and separated in the intervening 

 portion of its course. In Pyrrhulopsis splendens and P. 'jj^rsonata the thyrohyoideus 

 arises from the inner surface of the parahyal process anterior to the insertion of the 

 stylohyoideus on the outer surface ; in most Parrots the two muscles are attached 

 opposite each other. 



In Cyanorhamplms, Prioniturus, Caica, Pfistes, JSymphicus, and Psejphotus there are 

 no special features worthy of notice. 



In Pionopsittacus pileatus a thyrohyoideus is absent. In Psiftinus incertus the 

 muscle is also absent, unless one which has the insertion of a thyrohyoideus, but the 

 origin of a thyroglossus, be regarded as the muscle which has changed its origin. 



The absence of the muscle in Pionopsittacus and its attenuation in others would 

 seem to indicate that in some it is undergoing retrogression. 



In Lorius domicella (Pis. XXVII. & XXIX. figs. 21 & 50) and L.flavo-palliatusthe 

 muscle arises from the anterior end of the crura of the parahyal arch, immediately 

 behind the hypocleidium, and is inserted in a somewhat oblique fashion into the dorso- 

 lateral surface of the thyroid, being covered at its insertion by the thyroglossus. In 

 Eos riciniata the muscle is similar in its relations^but it is confluent at its origin with 

 the thyroglossus. In Vini australis the muscle is confluent both at its origin and 

 insertion with the thyroglossus, though free elsewliere. 



' The artist, however, has represented the two muscles as distinct at tbeir posterior extremity. 



