106 MR. W. K. PARKER ON THE STRUCTURE 



aborted anterior head, comparable to tbe " tubercle " of a rib, and answering to the 

 short eras of the incus, has been left free. The anterior head, or " suprastapedial" (s.st), 

 is, however, continuous permanently with the auditory capsule in Sphenodon (Huxley, 

 " On Malleus and Incus," p. 397, fig. 4, S.St), and also, as I find, in the Bull-frog {Bana 

 pipiens). Notwithstanding that in Sphenodon the posterior head is free, and the anterior 

 is fixed, contrary to what is here shown in the Chelidon, yet in these two, the adult 

 Lizard and the embryo Bird, the " extrastapedial " (Plate XX. fig. 7, est, and Huxley 

 op. cit. fig. 4, E.St) has a similar shape; even the foramen seen in Sphenodon (a) soon 

 appears in the Bird. The " infrastapedial " (Plate XX. fig. 7, ist) of this young bird 

 is longer than I found it in the Powl, even after the oval tract of ear-wall had come 

 away with its " mediostapedial " stalk. This is not all; for its pointed apex is con- 

 tinuous with a band of cells of indifferent tissue which runs downwards towards the 

 entering carotid artery at the skull-base. 



In Sphenodon (op. cit. fig. 4, Sth) the scooped " extrastapedial " passes directly down- 

 wards into a bar which is labelled Sth (stylo-hyal) ; but in the Crocodile (op. cit. 

 figs. 1 & 2, Sth) the stylo-hyal is a short club of cartilage, flattish, with its broad end 

 upwards, looking backwards, and having a clear membranous space between it and the 

 " extrastapedial." 



The stylo-hyal of Chelidon answers to this description exactly ; and if the reader will 

 turn to Professor Huxley's figure in this part of the Powl (op. cit. fig. 5, A, B, I.St) he 

 will see that it is there, but that it has become confluent with the infrastapedial. In 

 figs. 5, 9, & 10, st, of my former paper, this part is not shown ; but in a chick one day 

 older (fig. 14, i.st) it is certainly figured, but not distinct. Not having seen it in the 

 earlier stage, I could not choose but find it in the next, as it had then coalesced with 

 the " infrastapedial." In certain birds this part ossifies ; and this fact led me to call it 

 the " stylo-hyal" *. The distal part only of the rest of the arch is chondrified, namely, 

 the small cerato-hyal (chy), which, with its fellow, lies in the substance of the tongue. 

 The basal element, " basi-urohyal " (bhy, bbr), is a stout wedge, which narrows, and 

 then is fiat and emarginate behind. The so-called " thyro-hyals " (= 1st branchials, br l ) 

 are very large, the upper or proximal piece embracing the occiput. In this illustra- 

 tion the lingual skeleton is drawn as flattened out in the minute preparation, so as to 

 display all the parts at once. 



I take this opportunity further to illustrate Professor Huxley's account of these parts 

 in his invaluable paper (op. cit. p. 398), and first give the condition of these parts in a 

 fledgling Crow (Corvus corone). The membrana tympani (fig. 8, mty) is shown from, 

 the inner side, with the stapedial and mandibular structures ; the articular end of the 

 lower jaw is shown slightly dislocated, and the " siphonium " is cut through. 



This tube, the siphonium of Nitzsch, conveys air, not from the quadrate to the lower 

 jaw (see Huxley, op. cit. p. 391), as in the Crocodile, but it directly opens into the 

 tympanic cavity in the Birdf. 



* Full often have I argued with the author of the paper just quoted that this dilated, decurved, sometimes bony 

 extremity of the hird's " infrastapedial" was the true " stylo-hyal;" hut he always turned his deaf ear towards 

 me. / am silent now ; but " he will rise up at the voice of the bird," so sharp and clear. 



t The dissection here figured was made to dispel a doubt of Professor Huxley's as to the correctness of Nitzsch's 



