290 



Appendices to Fifth Annual Report 



lower by a narrow aperture. It is with the lower chamber that the 

 duct from the swim-bladder communicates, and it is it that the horizontal 

 semicircular canal principally encircles. The basisphenoid is similar to 

 the herring's, but it has a stronger vertical spine, and the transverse part 

 is more like the salmon's, sloping slightly upwards to each side. The 

 part surrounding the foramen of the oculo-motor nerve below is a mere pro- 

 cess. The thickening of this process to an equal size with the upper trans- 

 verse part causes the herring's basisphenoidal arms to appear horizontal ; 

 while its great enlargement in the shad causes the bone to appear to grow 

 downwards on each side, and thus gives it its horse-shoe shaped form. The 

 anterior supraorbital part of the orbito-sphenoid is single for only a small 

 part in the middle of its length, although the two sides lie close to one 

 another. It passes back like the shad's, to meet the median part of the 

 ectethmoids. The mesethmoidal ridge shows ouly the slightest emargina- 

 tion at its anterior tip, being therefore much more like the herring's than 

 the shad's; there is a foramen underneath or through the ridge, just 

 behind its anterior end. The ectethmoids are even of a more irregular 

 shape than the herring's. From the median part there projects downwards 

 and laterally a thin flat process forming the anterior upper boundary 

 of the orbit ; lying across the upper corner of this process, and 

 mostly projecting backwards over the eye, is a thin depressed scale-like 

 piece ; while from its inner anterior corner there project two sharp-pointed 

 narrow processes, one dorsal lapping forwards externally over the 

 ethmoidal splints, and one passing downwards and outwards along the 

 ethmo-palatine cartilage. The paraspheroidal wings are longer, less deep, 

 and more pointed than the herring's. The vomer, long and delicate, has 

 no teeth. The nasal is larger than the herring's, and the internasal 

 cartilage is very thin, and the nasal capsules smaller than in the herring. 

 The frontals are wider anteriorly, and therefore closer to one another 

 mesially. The form of the quadratje and metapterygoid is intermediate 

 to those of the herring and shad, the foramen seen in the shad being in 

 the pilchard smaller, and forming a narrow slit between the quadrate and 

 metapterygoid; the median part of these bones is, however, very delicate and 

 thin. The symplectic is a delicate rod. The tongue has a bony scale, bearing 

 very slight teeth (Day and Giinther say the tongue has no teeth). The 

 neck of the maxilla is more slender, the lateral part narrower and very 

 slightly if at all toothed. The septo-maxillary is wider and shorter, 

 scarcely attached to the maxilla, but overlapping and fixed to the jugal with 

 its lower end. The pre- and inter-opercular bones are very firmly attached 

 to the articular. The operculum has about six radiating ridges on it like 

 those of the shad, and has a more horizontal lower margin, while the 

 operculum is of an oblong form, and nearly right angled. The anterior 

 branchiostegals are rather wider, less rod-like, than the herring's. The 

 posterior one is peculiar in being continued with a curve upwards and 

 backwards of nearly its full width to underlap the suboperculum ; it is 

 therefore a longer bone than the interoperculum, though not extending 

 quite so far forwards, and it is but loosely attached to the epihyal- I 

 have found seven branchiostegal rays (Giinther gives six, Day six to eight). 

 The epihyal is longer relatively to the ceratohyal than is the case in the 

 herring. The urohyal is relatively longer and less deep, but has the strong 

 lateral ridges like the shad's. The first branchial arch has approximately 

 28 busi- and hypo-, 45 cerato-, and 38 epi-branchial rakers ; the second 

 arch has 45, 45, and 50 respectively ; the third has 36, 50, 53 ; the 

 fourth arch has 65 hypo- and cerato-, and 45 epi-branchial rakers ; it has 

 also about 35 posterior short rakers. The fourth and fifth arches are 

 curiously modified. The fourth epibranchial (upper pharyngeal), which is 



