of the Fishery Board for Scotland. 



289 



form the upper margin of the foramen. The hyomandibular does not 

 articulate along its whole upper edge with the pterotic and sphenotic, but 

 forms a single articulation with each of these, its two upper corners 

 only being raised into distinct condyles. The lower jaw and most of the 

 membrane bones of the skull are like the herring's, but generally stronger. 

 The upper surface of the frontals is much more deeply sunk posteriorly 

 behind the forebrain, and forms there a tri-radiate- bottomed depression. 

 The maxillae are less sharply toothed, and the gape is relatively less, while 

 the premaxilke, instead of meeting mesially to form a straight anterior 

 border, are curved inwards at their symphysis, so as to leave a rather 

 deep notch between them, into which fits the lower jaw. This notch 

 forms a good external specific distinction from the herring. The nasals, 

 though not longer, are stouter than the herring's. The orbital bones are 

 the same in number as the herring's, and the opercular apparatus is 

 similar, except that the external face of the operculum has a striated 

 appearance, from the presence of several mucus-canal thickenings which 

 radiate downwards and outwards from its articular head. 



The branchiostegal and branchial arrangement is like the herring's, but 

 there is more cartilage surrounding the edge of the enlarged (4th) pharyngo- 

 branchial, and the number of rakers differ, being 12 hypo- 14 cerato- and 

 14 epi-branchials on the first arch; on the second, 12, 13, 12; on the 

 the third, 12, 12, 10; and on the fourth, 3, 12, 10, the fourth also having 

 about 14 posterior short rakers interlocking with about 10 on the fifth 

 arch. The tongue and basi-branchials are unprovided with teeth. The 

 urohyal has a strong median longitudinal ridge along each side. 



The Pilchard (Olupea pilchardus). 



In the pilchard's vertebral column there are no important variations from 

 that of the herring except that the arrangement of the more posterior zyga- 

 pophyses is more like that of the shad. I find 19 caudal rays, 18 dorsal, 

 17 pectoral, 8 ventral, and 18 anal, which agrees with Day's record. The 

 vertebras number about 52 (Day gives 50, Giinther 53, Lowe 50-51), and 

 the first complete haemal arch is on the 21st. There are 32 ribs. The 

 loose bones attached to the back of the skull are more numerous than in 

 the shad or herring, there being a great mass of them principally arising 

 from only one head attached to the posterior tip of the epiotic. 



The skull is rather narrower posteriorly, and considerably shallower 

 from above downwards. The single hollow formed on the posterior 

 external surface slightly above and on each side of the foramen magnum 

 by the exoccipitals and epiotics in the herring is in the pilchard divided 

 into two halves by a ridge which runs down from the inside of the 

 epiotic ' elbow ' towards the foramen, before reaching which, however, 

 it dies away in the exoccipital. On account of the greater flatness of 

 the cranium, the postero-lateral cavity is smaller and the dorso- 

 lateral foramen shallower. The posterior semicircular canal scarcely 

 enters the supraoccipital. The posterior process of the pterotic is more 

 delicate and sharper pointed, while the process of the prootic is rather 

 longer, thinner, and rod-like, and projects more outwards. The anterior 

 (prootic) air vesicle is more elongated (laterally) than the herring's, 

 and the upper part of the posterior air vesicle seen externally at the 

 base of the postero-lateral cavity, and also showing beneath the edge of 

 the pterotic, is larger and more prominent. This is owing to the single 

 spherical vesicle of the herring having nearly become double in the 

 pilchard, the upper and larger part being connected to the smaller and 



