of the Fishery Board for Scotland. 



291 



flattened like the herring's, bears gill filaments and long rakers on its 

 anterior side, and also the posterior half of a curious comb-like organ. 

 The fifth arch has a cartilaginous epibranchial strip, which is attached to 

 the anterior edge of the flattened 4th epibranchial, and bears the anterior 

 half of the comb-like organ. This organ is of an oval form by the 

 apposition of its two parts, which each have a convexo-concave form, the 

 concavity, however, being slight, so as to leave only a small intermediate 

 space. Each of these segments is covered from end to end by a series of 

 transverse very close-sitting thin laminae or teeth. These are of a V-shaped 

 form, one arm being longer than the other, and the apex in particular- 

 being attached to the body of the organ. There are from 100 to 150 of 

 these laminae side by side on each segment. The whole organ, i.e., the 4th 

 posterior epibranchial comb and the 5th anterior ditto approximated, 

 together cover the whole under surface of the 4th flattened epibranchial 

 (or superior pharyngeal), and form a pouch lined internally by the series 

 of teeth described. 



The Sprat (Clupea sprathis). 



In the sprat the vertebral column consists of only 48 vertebrae, and 

 variations from this number seem to be fewer than is the case with the 

 herring. The arrangement of neural and haemal spines, ribs, and inter- 

 musculars is similar to that of the herring, but the numbers are fewer in 

 correspondence with the reduced number of vertebrae. The ribs number 

 about 28 in all, the first being, as in the herring, on the 3rd vertebra, and 

 16 only are fixed. The first complete haemal arch is on the 18th vertebra. 

 The prominent articular processes (zygapophyses) found in the herring, 

 especially on the caudal portion of the column, are absent in the sprat. 

 The transverse processes (rib appendages anteriorly) are found about 

 as far back as the 28th vertebra. The fin rays vary in number, but the 

 normal condition gives 16-18 dorsal, 16 or 17 pectoral, 17-19 anal, 7 

 ventral, and 19 caudal. The skull in its general appearance is more 

 like the herring's than either the pilchard's or shad's, the form and arrange- 

 ment of the bones forming the posterior aspect and side of the cranium 

 being very similar. There is a relatively more prominent anterior air 

 vesicle situated in the prootic, and the auditory fenestra extends nearer to 

 it than does the herring's ; but no posterior air vesicle is developed. The 

 supraoccipital has a distinct fold on its internal surface beneath the 

 external dorsal laterally radiating ridge, and the two sides of this fold 

 almost or altogether meet to form a short canal similar to the fold or 

 complete canal formed as in the herring on its posterior outer surface 

 and continuous with the epiotic. The latter, as in the herring, contains 

 the upper part of the posterior semicircular canal, while the former 

 embraces the upper part of the anterior horizontal canal. These aper- 

 tures open close together just above the junction of the anterior and 

 posterior membranous canals. The opi^thotic is even smaller than 

 the herring's. The basisphenoidal vertical spine is relatively rather larger 

 than the herring's, and the parasphenoidal wings are more pointed and 

 slightly emarginated posteriorly, like the pilchard's. The vomer has a 

 short ventral ridge on it, but no teeth. The ethmoidal bones are like the 

 herring's, the median ridge not being terminally bifurcated. The maxillae 

 are finely toothed, as are the premaxillae, but the palate has no teeth on it. 

 The metapterygoid has, however, on the outer side of its narrow under surface 

 a very slight short ridge, with a few delicate teeth. These are not readily 

 discernible inside the mouth, but if felt might be mistaken, without dissec- 



