OF THE TONGUE OF PAEEOTS. 263 



sheath and partly from the uro-hypobranchial tendon ; in Cyanorhamphus and Stringops 

 it arises mainly from the uro-hypobranchial tendon, and in Gahjptorhynclms chiefly 

 from the urohyal sheath. In Chrysotis (PL XXVIII. fig. 28), Caica, and Beroptyus 

 it arises in main part from the anterior two-thirds of the urohyal, and to a small extent 

 from the posterior border of the basihyal. In Ara, Poeocephalus robustus, Lorius- 

 (Pl. XXIX. fig. 37, ch.), Eos (PI. XXIX. fig. 39), and Vini it arises in part from the 

 nodule on the ventral surface of the urohyal, and in part from the uro-hypobranchial 

 tendon. 



In Pezoporus and Pyrrhulopsis there is developed along the inner side at the anterior 

 end of the muscle a small tendinous tract, which extends about half its length. 



In Eclectus, Am, Cacatua triton, and C. alba the muscle is inserted along the 

 anterior half of the hypobranchial. In Microglossits, Prioniturus, Cacatua galerita, 

 C. leadbeateri, and C. roseicapilla it is inserted into the anterior two-thirds; and in 

 Pyrrhidopsis, Nestor, and Calyptorhynclms into the posterior two-thirds. In Lorms 

 (PI. XXIX. fig. 37), Eos, Vini, Brotogerys (PI. XXVIII. fig. 33), Loriculus, Conurus 

 holochlonis, Nasiterna, Psittacus, Ptistes, Psittinus, Poeocephalus, Pezoporus, Stringops, 

 Calopsittacus, Peroptyus, and Chrysotis it is inserted along nearly the \vhole length 

 of the bone. 



The Mesoglossus Muscle. 



This muscle has not been previously described. It is triangular in form, with its 

 apex directed backwards, and connected with the superior ceratoglossals in a manner 

 already described {ante, p. 227). It lies in the dorsal concavity of the entoglossum 

 ( PI. XX VI. fig. II, mg., and PI. XXIX. fig. 50, mg.), and is attached on the one hand to 

 the superior ceratoglossals, and on the other to the hypoglossus rectus and the membrane 

 of the extremity of the tongue. In comparatively very few Parrots it is wholly 

 muscular in nature ; in the greater number it is composed of muscle-fibres and a 

 dense connective tissue, in varying proportions, inextricably mixed together; in yet 

 a large number still it is wholly composed of connective tissue of a very dense and 

 resistant nature ; and in one or two it is represented by a connective-tissue membrane 

 only. The muscle, or that which represents it, is invested by a thick fascia. 



In Nestor (PL XXVII. fig. 22, mg^.) and Calyptorhynchus the muscle is not represented, 

 except by a thick membranous sheet of white fibrous tissue. In Platycercus, Cacatua 

 (PL XXVII. fig. 13, mg^.), Conurus, Calopsittacus, Psittinus, Stringops (PL XXVII. 

 fig. 18), Pyrrhura (PL XXVII. fig. 19), Psittacula, Bolborhynchus, Cyanolyseus, and 

 Brotogerys it is represented by a mass of dense, white, fibrous tissue, invested in a 

 tough sheath ; in the tissue of Cacatua triton branched pigment-cells are present. In 

 Microglossus, Pyrrhulopsis, Eclectus (text-fig. 7, p. 231), Pakeornis, and Tanygnathus 

 muscles-fibres have appeared in the mass of fibrous tissue ; in Chrysotis (PL XXVII. 



