542 H. H. SWINNRBTON. 



and is in direct coutacfc with the pre-ethmoid cornn, whilst 

 still lacking relationship to the parethmoid {e. p. c). These 

 features are much better seen now that the ethmoid region 

 has begun to elougate. Beyond the articulation with the 

 pre-ethmoid cornu the palatine sends a small projection, the 

 future maxillary process, forwards on to the upper end of the 

 maxilla. 



A fusion o£ the quadrate cartilage with the hyoid arch, 

 such as that seen by Pollard (94, p. 19) in Bleunius and 

 Gobius, is nowhere indicated. 



Of the osseous elements belonging to these two arches, 

 all, except the palatine and pterygoid, have appeared in the 

 older larvae of the stage. 



Stage IV, — As with the cranium, so with the visceral 

 skeleton, this stage is distinguished chiefly by the presence of 

 nearly all the osseous elements possessed by the adult, and of 

 most of the cartilaginous ones. Except when otherwise 

 stated, the ossification of a cartilaginous portion must be 

 taken to mean that only the surface is ossified, whilst the 

 cartilage inside remains intact. 



In the branchial apparatus (fig. 16) the copulare commune 

 has become ossilied in three places, and thus the same number 

 of basibranchials {hr. h. 1—3) are recognisable. Apart from 

 this it has undergone no further change except, perhaps, for 

 a slight tendency on the part of the unossified cartilage to be 

 less hyaline than the rest. The first basibrauchial {br. h. 1) 

 sends obliquely backwards and downwards from its ventral 

 surface a strong osseous process tipped with cartilage for the 

 articulation of the urohyal. The second and third basi- 

 branchials (br. b. 2—3) remain simple, and the fourth {br. b. 4) 

 is still separate, small, and cartilaginous. Each lies in front 

 of the arch to which it belongs. 



The hypobranchials (br. h.) of the first three arches and 

 the flattened ventral extremity of the fourth are still wholly 

 cartilaginous. All the cerato-branchials are ossified, and in 

 case of the fifth, except for a small portion at the lower end, 

 all the cartilage has disappeared. Thus, though it was 



