162 DE. ST. GEORGE MIVART ON TUE [Mar. 5, 



The following papers were read : — 



1. On the Hyoid Bone of certain Parrots. 

 By St. George Mivart, F.R.S. 



[Eeceived March 4, 1895.] 



Distinctive structural characters are so ranch needed for the 

 classification of birds, that I think the following descriptions and 

 illustrations of some skeletal structures, which, so far as I know, 

 are now described and figured for the first time, will not be un- 

 welcome to Ornithologists, if not to other naturalists also. 



The structure of the hyoid in certain birds was described as 

 long ago as 1835 by G. L. Duvernoy (Mem. de la Societe d'Hist. 

 nat. de Strasbourg, tome ii.), who figured those of Ara ararauna and 

 Coracopsis vasa. In 1858 C. Giebel (Zeitsch. gesammt. Xaturwiss. 

 Band xi. pp. 42 & 43, Taf. v. & vi. figs. 35—41) gave repre- 

 sentations and descriptions of the hyoid of the follo\nng species 

 as named bj^ him : — Psittams rufrostris (fig. 35), P. erithacus 

 (fig. 36), P. oclirocephaJus (fig. 37), P. leucocephalus (fig. 38), 

 P. menstruus (fig. 39), P. sinensis (fig. 40), and P. cristatus (fig. 41). 

 Dr. Gadow (1891) has also described and figured (Bronn"s Thier- 

 reich, Band vi. Abtheilung iv., Anatomischer Theil, pp. 298, 

 299, and 302, plate xxx. fig. 20) the hyoid of a species of Ara. 



Having lately directed my attention to the skeleton of the 

 Lories, I Avas very desirous to examine the hyoid in species of 

 that family, in order to compare them with that of Psittacus 

 erithacus, taldng the latter as my type of Parrot- structure. 



Through the kindness of our Prosector, Professor Beddard, 

 P.E.S., I have received for examination the hyoid bones of Psit- 

 tacus erithacus, Lorius domicella, L. Jlavopalliatus, Eos reticulata, 

 E. indica, Tric/ior/lossus ornatus, and Stringops liahroptilus. 



So far as I have been able to ascertain, the whole order Psittaci 

 is distinguished from every other order of birds by the shape of 

 its hyoid. The characters which, when taken together, seem 

 distinctive are : — 



(1) Basihycd much hi'oadened posteriorly. 



(2) Basihycd developing on either side a forwardly and upwardly 



directed process, which I propose to distinguish as a para- 

 hyal process. 



(3) An OS cntoylosium in the form of a single broad bone 



\\i\h. a considerable central foramen or, much more com- 

 monly, in the form of two lateral parts, entoglossals, 

 medianly united in front by cartilage and leaving a vacant 

 space between this and their attachment behind to the 

 basihyal. 



The real nature of these entoglossals (as 1 propose to call them) 

 is not eAadent to me. OA^en writes ^ of the ceratohyal as being 



* Anat. of Vertebrates, toI. ii. p. 57. 



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