OF THE TONGUE OP PAEROTS. 253 



Chrysotis cestiva, there are pigmented blood-capillaries, which, when microscopically- 

 examined, show the characteristic meshwork of muscular blood-capillaries; moreover, 

 the condition of the muscle in Strincjops is such as to leave no room for doubt as to 

 the nature of this tissue. 



The retrogression of the posterior portion of the muscle can be traced, step by step, 

 up to its complete disappearance in Nestor and Microglossus. It is strange that such 

 a generalized tongue as that of the latter Parrot should have reached, in respect of 

 this, the most advanced stage. 



(/3) Mijlohjoideus fosferior. — This muscle is composed of two portions — an inner, 

 more posterior serpihi/oideus {se.h.p.), and an outer, more anterior stijlohjoideus (se.h.a.). 

 In all Parrots, except the Loriidse, both portions are present, but in them the stylo- 

 hyoideus is absent; it will be shown that the Loriidean condition is specialized. 



The serpihyoideus and stylohyoideus arise from a common origin at the posterior 

 extremity of the mandible, and passing forwards as a single muscle for a greater or less 

 distance they separate, and the former becomes inserted partly into the nodule lying 

 on the ventral surface of the urohyal, or, in the absence of the nodule, into the sheatli 

 investing the urohyal, and partly into the uro-hypobranchial tendon, which is attached 

 at one end to the urohyal nodule (N.) and at the other to the head of the hypobranchial ; 

 the stylohyoideus turns outwards, passes round the lateral ceratoglossal, parallel witli 

 and in front of the sternohyoideus, and reaches its insertion into the outer lateral 

 surface of the paiahyal process. 



In Cacatua (F\. XXVI. fig. 4, se.h.), Conurus jendaya, C. cactorum, Psittacula, Cyano- 

 lyseiis, Ftisfes, Coracopsis, Bolborhynclms, Loriculiis, and Brotogerys (text-fig. 13) the 

 serpihyoideus is a single undivided muscle. In Cacatua galerita (PI. XXVUI. fig. 25) 

 the muscle sends a small tongue-like projection on to the ventral surface of the uro- 

 hypobranchial tendon, which nearly meets the origin of the ceratoglossus inferior anticus 

 accessorius, and another along the outer extremity of tlie tendon ; in C. foseicapiilla 

 tins inner tongue-like projection is much wider. In Pionopsittacus the muscle exhibits 

 a remarkable contraction of its substance at its origin, which is tendinous, and fore- 

 shadows the condition of that in Eos and Pezoporus. 



In Conurus holochlonis, Eclectus, Palceornis (PI. XXVIII. fig. 32), and Fyrrhura 

 (PI. XXIX. fig. 40) the serpihyoideus shows a very incipient division of the muscle 

 into an outer and inner portion, in the form of a slight, almost imperceptible thinning 

 of the muscle-fibres in the middle line at the anterior end of the muscle. In 

 Palceornis there is in addition a very slight plane of division continued backwards 

 from the thinned area, and more marked in the right than the left muscle. 



In Chrysotis (PI. XXVIII. fig. 28), Cacatua sulplmrea, Calopsittacus, Ara ararauna 

 (PI. XXVIII. fig. 24), Psittacus (PL XXVI. fig. o),Nasiterna, Caica, Cahjptorhynchus 

 funereus, and Tanygnathus the thinned area of retrogression is more marked and 



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