OF THE TONGUE OF PAEEOTS. 257 



appears to be nndergointj retrogression, for in many Parrots its origin is represented by 

 fascia alone, while in others its insertion is reduced to a functionless filament ; in 

 Pezoporus the muscle of one side of the tongue has disappeared and that of the other is 

 going ; and in yet a few others there is a general thinning of the muscle. In Lorius, 

 Eos, and Vini (the only three members of the Loriidse obtainable) the muscle has com- 

 pletely disappeared, the position of its insertion being indicated in one of them by 

 connective tissue (vestigial fascia) and in the others by a space upon the parahyal 

 process. 



In all Parrots, except the Loriidae, the outer portion of the serpihyoideus is inserted 

 to the uro-hypobranchial tendon, and does not extend beyond it, while in the Loriidse 

 it is prolonged forwards to an independent insertion at the postero-outer angle of the 

 basihyal. Thus the Loriidae are characterized by this extended insertion and by the 

 absence of the stylohyoideus muscle. 



Nestor occupies a position of isolation with respect to its hypocleidal insertion of the 

 stylohyoideus. 



There are indications, in the projection forwards of the parahyal processes beyond the 

 insertion of the stylohyoideus, in certain Parrots of an approach to the Loriidean 

 condition of a completed parahyal arch. 



There are all stages in the division of the serpihyoideus into two parts, from an 

 incipient thinning, localized anteriorly and barely perceptible, to a well-defined plane 

 of division passing the whole length of the muscle. In all Parrots but one, the two 

 portions of the muscle persist ; but in Nestor it is probable that the outer one has 

 disappeared. In certain Parrots the inner portion exhibits a remarkable contraction of 

 its substance at its origin, which in some is not tendinous, but in others markedly so; 

 Eos represents the highest specialization in this direction. 



Thus the muscle appears to be specializing in two directions : in one, by the 

 complete retrogression of the stylohyoideus, by the division of the serpihyoideus and 

 by the shifting forwards of part of its origin to the basihyal ; and in the other direction 

 additionally by the contraction of, and the subsequent formation of, a tendon at the 

 origin of the inner portion. 



As far as the characters of the tongue are concerned, we may say that within the 

 Loriidse — the most specialized family of Parrots — two lines of evolution seem to be 

 mapping themselves : the one exemplified by Lorius and Vhii, and characterized by an 

 uncontracted origin of the serpihyoideus and by the tendon of the ceratoglossus 

 inferior posticus not being fan-shaped at its origin from the muscle ; and the other by 

 Eos, characterized by the contracted origin of the inner portion of the serpihyoideus 

 and the fan-shaped ceratogiossal tendon. Conditions foreshadowing both these 

 characters of Eos are met with in certain of the less specialized Parrots. 



