288 



Appendices to Fifth Annual Report 



The anterior (prootic) air-vesicle is relatively larger than the herring's, 

 but the posterior is small, and indistinguishable externally. The duct 

 leading through the exoccipital to it is also very small in diameter. 



The point of bifurcation of this duct is at the junction of the exoccipital, 

 pterotic and prootic, and is overlapped by the opisthotic, which is larger 

 than the herring's, and has a much more pronounced backward process 

 giving attachment to the inner arm of the post-temporal. The lower 

 part of the posterior semicircular canal lies in the junction between the 

 pterotic and exoccipital, part of its diameter being in each. The median 

 bar of the orbito-sphenoid is much stronger than in the herring, and has 

 its full depth where it comes off from the paired part, instead of being 

 there as in the herring a narrow rod ; it passes forwards to be closely 

 attached to the ectethmoids, where it is again double, the two sides, 

 however, being closely applied to each other. 



The foramen below the basisphenoid is smaller, owing to the lower 

 lateral corners (beneath the aperture for 6th nerve) having grown 

 downwards along the sides of the alisphenoids. The basisphenoid is 

 therefore somewhat horse-shoe shaped, with the vertical spine passing 

 across its hollow. The alisphenoids face more outwards, and less directly 

 forwards than do the herring's, consequently their inner edges are more 

 anteriorly placed than in the herring, and the floor of the forebrain 

 (continued from the alisphenoids by the orbito-sphenoids) appears to reach 

 relatively rather further forward than does that of the herring. The 

 alisphenoids are not so circular in outline as the herring's. The anterior 

 edge meeting with the orbito-sphenoid is nearly vertical, their dorsal edge 

 horizontal, the posterior also nearly vertical, while the ventral curves 

 down from the lower anterior corner to form with the lower posterior 

 corner a short process articulating with the prootic. The dorsal anterior 

 corners of the paired part of the orbito-sphenoid nearly reach to the 

 posterior processes of the ectethmoids, and they form a shallow concavity 

 over the posterior part of the orbit, while as in the herring the median 

 bar appears in front of them as part of the interorbital septum. 



The ethmoid agrees with the herring's in having two lateral projections 

 posteriorly covering the cornua, while it passes backwards in a pair of 

 splint-like processes which just overlap the ectethmoids; but it differs in 

 so far as the median anterior portion, in place of forming a single median 

 ridge, stopping abruptly over the labials, divides into two flat processes, 

 which diverge laterally so as to give the termination of this bone a wide 

 V-shaped form, somewhat like that in the trout. The ectethmoids send a 

 splint nearly halfway across the orbits, and overlapped by the frontals. 

 They are separated by a very thin sheet of cartilage. 



The parasphenoidal wings are less deep and more pointed posteriorly, and 

 the teeth on vomer are less prominent and fewer than in the herring. The 

 pterygoid is thicker, less splint-like, and not so acutely angled. It spreads 

 out more at its anterior end over the cartilaginous centre of the bar. The 

 mesopterygoid is relatively shorter ; while the palatine is much stronger, 

 thicker, and the cartilage is more completely ossified than the herring's. 

 Its small ridge projecting into the mouth is said by Giinther to have no 

 teeth, but I have found a few slight teeth on it. The quadrate differs 

 from the herring's in so far as, instead of being triangular, it is roughly 

 L-shaped. The lower angle articulates with the mandible, the anterior arm 

 with the mesopterygoid, the lower upwardly inclined arm with the meta- 

 pterygoid. This form is easily explained; it occurs from the central part 

 and postero-dorsal edge of the herring's quadrate not being ossified, 

 leaving a membranous unossified nearly circular portion between it and 

 the metapterygoid, which has a slight emargination on its anterior edge to 



