544 H. H. SWINNERTON. 



p. 19) describes a similar sequence of events in the develop- 

 ment of this region in Blennius and Gobius, but is probably 

 inaccurate in speaking of a shifting of the stylohyal attach- 

 ment; it is not the stylohyal which shifts, but the hyo- 

 mandibular which elongates. The articular border of the 

 latter has differentiated still more distinctly into two articular 

 heads, which fit into corresponding facets (fig. 12, %»i."), the 

 hinder one on the pterotic, the front one between the pro-otic 

 and sphenotic. The intervening portion of the border has 

 thus become practically functionless for suspensory purposes. 

 Both these heads, as well as the opercular process (fig. 13, 

 hym.'), remain cartilaginous. Looking at the bone internally 

 (fig. 13) the hyomandibular nerve foramen {hym.f.) occupies 

 the same position as it did in the last stage, but externally 

 (fio-. 9) at first sight it seems to have disappeared; in reality 

 it has been carried to the ventral edge {hym. /.) by over- 

 growth of bone. 



Though the cartilaginous core of the symplectic (figs. 13, 

 39, .s'ym.) has undergone no change either in shape or thick- 

 ness, its osseous portion has sent out extensive laminae of bone 

 dorsally and ventrally ; consequently if no attention is paid 

 to the condition of the original cartilage an entirely false 

 idea of the true relationships of this bone will be gained. 

 Its distal end is still unossified, and lies almost completely 

 enclosed by the quadrate above, and by a long bony process 

 of the quadrate below. 



Under the symplectic, and at the level of the hinder end 

 of the process just mentioned, there is a small oblong 

 cartilage (figs. 39 and 40, x.) which is present only in 

 individuals Nos. 22 and 23, and is quite unrepresented 

 as far as I can ascertain in any individual larger or smaller 

 than these. I have been unable to determine its homologies. 

 That it is not a separate portion of the symplectic is proved 

 by its appearing' long after this is completely enclosed in 

 bone. Nor can it be regarded as an articular cartilage of 

 any kind, for none of the surrounding bones, all of them 

 more or less rigidly fixed, present anything which can be 



