314 AVES. 



the beak, in consequence of the union which cross each other at a considerable angle a dis- 



takes place between different small fibres as position which at first sight seems directly 



they pass from the circumference inwards. It opposed to the natural intention of a bill, 



is worthy of observation that the principle of With this singular disposition, the Cross-bill, 



the cylinder is introduced into this elaborate however, possesses the power of bringing the 



structure : the smallest of the supporting pillars points of the mandibles into contact with each 



of the mandibles are seen to be hollow or other ; and Mr. Yarrell, in his excellent paper 



tubular when examined with the microscope, on the Anatomy of the Beak of this bird, ob- 



The structure is the same in the lower man- serves that, notwithstanding M. Buffon's asser- 



dible (M, Jig. 150), but the fibres composing tion to the contrary, it can pick up the smallest 



the net-work are in general stronger than those seeds, and shell or husk hemp and similar 



of the upper mandible. seeds like other birds. He further shows that 



The medullary membrane lining these cavi- the disposition and power of the muscles is such 

 ties appears to have but a small degree of that the bill gains by its very apparent defect 

 vascularity. Processes of the membrane, ac- the requisite power for breaking up the pine- 

 companying vessels and nerves, decussate the cones that constitute its natural food. In a 

 conical cavity at the base of the beak. The air is pair of Cross-bills which were kept for some 

 admitted to the interior of the upper mandible time in captivity, one of their principal occu- 

 from a cavity (b, fig. 150) situated anterior to pations, Mr. Yarrell observes, " was twisting 

 the orbit, which communicates at its posterior out the ends of the wires of their prison, which 

 part with the air-cell continued into the orbit, they accomplished with equal ease and dexterity, 

 and at its anterior part with the maxillary A short flat-headed nail that confined some 

 cavity. The nasal cavity is closed at every strong net-work was a favourite object upon 

 part except at its external and internal aper- which they tried their strength, and the male, 

 tures by the pituitary membrane, and has who was usually pioneer in every new exploit, 

 no communication with the interior of the succeeded, by long-continued efforts, in draw- 

 mandible.* ing this nail out of the wood, though not 



The horny sheath of the mandibles in the without breaking off the point of his beak in 



Hornbills and Toucans is so thin that it often the experiment. Their vinceasing destruction 



becomes irregularly notched at the edge from of cages at length brought upon them sentence 



use. The Hornbills have, besides, upon their of banishment." He concludes his memoir by 



enormous beak, horn-like prominences of the observing that " the remarks of Buffon on the 



same structure and of different forms, the use beak of this bird, which he characterizes as 



of which is not known. * an error and defect of nature, and a useless 



The Trogons, Touracos, Buccos, &c. exhibit deformity/ exhibit, to say the least of them, 



forms of the bill which are intermediate to that an erroneous and hasty conclusion, unworthy 



of the large but feeble bill of the Toucans, and of the spirit of the science he cultivated, 



the short, but hard, strong, and broad bill of During a series of observations on the habits 



the Parrot-tribe, which is also hooked, so as and structure of British Birds, 1 have never 



to assist in climbing, like a third foot: (Jig. met with a more interesting or beautiful ex- 



128.) ample of the adaptation of means to an end 



The short, conical, and vaulted beak of the than is to be found in the tongue, the beak, 

 Rasores (Jig. 121) serves to pick up with due and its muscles, in the Cross-bill." * 

 rapidity the vegetable seeds and grains which The tongue, as has been already observed, 

 constitute their food, as well as small insects, can hardly be considered as an organ of taste 

 as ants, &c. with which the young are frequently in Birds, since, like the mandibles, it is gene- 

 nourished, rally sheathed with horn. It is principally 



The bills of the small Insessorial or Pas- adapted to fulfil the offices of a prehensile 



serine birds present every gradation of the organ in association with the beak, and it pre- 



conical form, from the broad-based cone of the sents almost as many varieties of form. Orni- 



Hawtinch to the almost filamentous cone of the thologists have not yet perhaps derived all the 



Humming-birds (Jig. 117, 125), and each of advantages which a study of the modifications 



these forms influences the habits of the species of the tongue might afford in determining the 



in the same manner as in the larger birds. The natural affinities of birds. 



short and strong-billed Insessores live on seeds The os hyoides very much resembles that of 



and grains ; those with a long and slender bill Reptiles. Its parts have been minutely studied 



on insects or vegetable juices. If the slender by Geoffrey St. Hilaire, who has bestowed 



bill be short, flat, arid the gape very wide, as upon them separate names: (a,fg 151) is the 



in Swallows, the bird takes the insects while glosso-hyal, b the basi-hyal, d d the apo-hyals, 



on the wing (fp. 118); if the bill be elongated e e the cerato-hyals, c the uro-hyal. The 



and endowed with sufficient strength, as in the body, or basi-hyal element, is more thickened 



Hoopoes, it serves to penetrate the soil and than the rest : in some birds it is cylindrical, 



pick out worms, &c. The length of the tongue depends chiefly on that 



Of all bills, the most extraordinary is that of of the lingual process or glosso-hyal element, 



the Cross-bill, in which the extremities of the In most birds it is lengthened out by a carti- 



mandibles curve towards opposite sides and lage ' appended to its extremity. This is re- 

 markable in the Swan and other Lamclli-rostres. 



' See Anatomical Appendix to Gould's Mono- 

 graph on the Rampkasttdae t fol. * Zool. Journal, vol. iv. p. 464. 



