CHONDROCRANIUM OF THE LARVAL HERRING. 



1221 



The foramen of the hyoid branch of the Yllth (facial) nerve is 

 situated as in the 5 mm. stage. 



At the posterior end of the hyomandibular, at the bottom, 

 there articulates with it the ceratohyal, by means of a conspicu- 

 ous knob, probably the appearing stylohyoid, as in Syngnathus, 



Text-figure 5. 



Dorsal view of branchial arches. 10 mm. Stage. X 60. 



The ceratohyal runs forward as far as the anterior end of the 

 ethmoid plate ; arising from the anterior end of the ceratohyal 

 are the branchial arches. 



The accompanying figure is of the bx-anchial arches of a larva 

 at this stage ; the figure is self-explanatory. 



c. The 20 mm. Stage. 



This description is based on reconstruction of a 20 mm. 

 specimen of Glupea harengus (text-fig. 6) 



At its extreme anterior end the ethmoid plate is, as in the 

 10 mm. stage, a flat plate; a little further back a median dorsal 

 ridge appeal's. This ridge runs back as far as the two lateral 

 protrusions, which are considerably developed. 



The ethmoid plate now becomes comparatively thinner ; the 

 pituitary foramen is also comparatively smaller. The post- 

 orbital processes are thicker, and run forwards beyond the lateral 



Proc. Zool. Soc— 1922, Ko. LXXXI. 81 



