OF THE TONGUE OE PAEEOTS. 25-S 



In Ara (PI. XXVIII. figs. 24 & 27), ^^estor (PI. XXIX. fig. 46), and Pionoj^sittacus 

 the two muscles are not confluent at any portion of their course, though they arise side 

 by side from the posterior extremity of the mandible. In Am ararauna the stylo- 

 hyoideus crosses the ventral surface of the serpihyoideus just after its origin. 



In Palceornis, Eclectus (PI. XXIX. fig. 49), Bolhorhynclius, Psephotus, Ara ararauna 

 (PL XXVIII. fig. 24), Conurus jewlaya, Caoatua, and Chrysotis the stylohyoideus 

 exhibits a slight retrogression of its muscle-fibres at its origin, the fascia remaining. 

 In Ara macao (PI. XXVIII. fig. 27), Conurus cactorum, Pezoponis (PI. XXIX. 

 fig. 47), PceocepMlus, Pionopsittac^is, and Stringops (PL XXVIII. fig. 26) the retro- 

 gression is more considerable, and in Stringops and Pezoponis it practically involves 

 the vphole origin and a considerable portion anteriorly to that. In Pezojiorus tlie 

 whole of the left-hand muscle has retrogressed and not a trace of it can be found, 

 while, as already indicated, the origin of the right-hand one has practically disappeared ; 

 the insertion has also retrogressed, for it is represented (Pi. XXVI. fig. 8) by a mere 

 filament of connective tissue, and the muscle can be, therefore, of no functional value. 

 In Nymphicus the insertion is also reduced to the condition of a mere filament. In 

 Platycercus (PL XXVI. figs. 5 & 11) also the muscle is very thin and suggestive of 

 an early disappearance. In Pionopsittaeus (PL XXIX. fig. 43) there is the same 

 advanced retrogression, for its origin is gone and its insertion nearly so. 



In Lorius (text-figs. 12, 14), Vini, and Eos (PL XXVI. fig. 1) the condition fore- 

 shadowed in Pezoporiis has been attained, for the stylohyoideus is absent on both 

 sides. In all three there is a vacancy on the parahyal arch (PL XXVII. fig. 21, 

 P.A.) lying between the origin of the thyrohyoideus [th.h.) and the insertion of the 

 serpihyoideus {s.h.), which corresponds in position with the insertion of the muscle in 

 those Parrots in which it is present ; and in Lorius there is attached at this part a 

 sheet of connective tissue, ribbon-like in form and of but short extent, which probably 

 represents the last remains of the fascia of the muscle. 



In Nestor (Pis. XXVII. & XXIX. figs. 22 & 46, st.h.) the muscle is very thin and 

 its insertion is unlike that in any other Parrot, and in respect of which it stands 

 alone ; it is inserted to the hypocleidium of the completed parahyal arch, immediately 

 antei'ior to the insertion of the sternohyoid eus. 



In the majority of Parrots the stylohyoideus is inserted at the apical portion of the 

 parahyal processes ; but in Pyrrhulopsis, Loriculus, Pezoporus, Cyanorhamphus, and 

 Tanygnathus it is inserted behind the apex, so that the free extremities of the para- 

 hyal processes extend some little way beyond the anterior margin of the insertion of 

 the muscle. And in Cyanorhamphus and Pyrrhulopsis the free portions of the processes 

 curve inwards towards the middle line, and in the former Parrot almost meet each 

 other ; it strongly suggests a growing forwards of the parahyal processes in order to 

 form the completed parahyal arch of the Loriidse and Nestor. 



