58 JfR. W. K. PARKER ON THE STRUCTURE AND 



The middle and outer ears (Plate 8, figs. 1-4, and Plate 9, figs. 8-14) are in a high 

 state of development; externally, the annulus {a.ty.) is almost an inch across, and is 

 complete ; its greatest width, below, is fully a quarter of an inch ; it is thick-rimmed, 

 unusually wide at the junction of its " horns," and altogetiier unique in size and 

 finish. 



The " columella " also is unique as to its development, having an osseous shaft in its 

 extra-stapedial (Plate 9, figs. 8, 9, 10, e.st., e.st'.), w^hich is not seen in other Batrachia. 

 The stapes and the dorsal pai't of the columella lie in a deep hollow, in the hinder 

 part of which is the fenestra ovalis (Plate 9, fig. 8). The stapes (st.) is oval, obliquely 

 truncate in front, and thick and convex externally. 



Against it, and somewhat within, lies the thick, short inter-stapedial (i.st.), whose 

 distal half is bony ; it is quite segmented from the medio-stapedial (m.sf..) which is 

 long, phalangiform, thick proximally where it is not quite ossified, and narrow and 

 arcuate further forwards. Then comes a short cartilaginous tract which is followed by 

 the extra-stapedial (e.st.) whose proximal part is ossified as a styloform shaft bone 

 {e.st'.), the cartilage within being also considerably ossified beyond the ectosteal tract. 



On the inner side, near the dilated end the supra-stapedial [s.st.) is given off at a 

 sharp angle, it passes upwards and backwards and is confluent with the cartilage lining 

 the tegmen tympani ; it is nearly as broad as the main bar, and is entirely unossiried. 



This division of the columella into three segments is of great interest, and can be 

 understood only by comparison with the state of things seen in the upper hyoid region 

 of Fishes in various groups. 



In the Chimseroids (see Hubrecht, fig. 2, hi/".) there is a " pharyngo-hyal" above 

 the "epi-hyal" {hy'.), but this topmost piece, so constant in the branchial arches, 

 proper, is not found in the hyoid of other Fishes. Much lower down, towards its 

 distal end, the epi-hyal (" hyomandibidar ") is cut off as a short distinct cartilage in 

 the Sturgeon'and Paddle-Fish. 



In osseous Fishes this cartilage acquires an additional bony sheath — the "symplectlc" 

 — but is not cut off. 



I am now perfectly satisfied that this lower subdivision of the " epi-hyal" element is 

 a secondary segmentation, such as is seen in the " pharyngo-branchials" of the 

 Sturgeon, where each cartilage is sub-divided into two pieces.'" 



In illustration of tliis we see that the " hypo-hyal" of osseous Fishes has two bony 

 centres ; in the Menopome it breaks up into three patches of cartilage. 



Therefore we see that the middle ear of this Frog has parts that correspond to the 

 following morphological elements of the upper part of the hyoid arch in the Fishes : — 



1. Pharyngo-hyal = inter-stapedial. 



2. Epi-hyal, subdivided into— a, hyo-mandibular=:medio-stapedial ; and h, sym- 

 pletic = extra-stapedial . 



* Mr. Howes pointed out this to mc, as shown in his excellent di.ssections at Sonth Kensington. 



