of the Fishery Board for Scotland. 



287 



the palato-pterygoid and hyoid arches is. very similar, as are also the otic 

 bones, the opisthotic in both cases being small — the more prominent opis- 

 thotic of the salmon being very similar to the pilchard's. The basisphenoid, 

 however, shows a considerable variation from its more strongly developed 

 counterpart in the salmon. The internasal cavity of the salmon is wanting 

 in the herring, and its cartilaginous interorbital septum appears in the 

 latter as membranous. The skeletons of the shad, pilchard, and sprat 

 bear a close resemblance to that of the herring. 



The Shad (Clupeafinta). 



The shad has a similar number of vertebrae to the herring ; I have 

 counted 56, Day records 55 to 56, and Giinther 56. The additional 

 degenerated vertebra) around the upturned part of the notochord, and the 

 arrangement of the bones (neural and hypural) of the tail also are 

 similar. The haemal articular processes (anterior ventral zygapophyses) 

 become longer and longer to nearly the end of the vertebral column ; 

 from about the 43rd vertebra to the end they are so long as not only to 

 pass forwards beyond (and beneath or inside) the posterior vertebral 

 zygapophyses, but they extend forwards so far as to allow of their tips 

 touching the base of the previous haemapophysis; they each thus lie 

 parallel to, and along the whole length of the preceding vertebra, and so 

 closely applied to it as to almost appear part thereof. The neural articular 

 processes are nearly as pronounced, and the posterior part of the vertebral 

 column is, therefore, correspondingly laterally strengthened. The first 

 complete haemal arch is situated on the 20th vertebra, and the ribs, there- 

 fore, are fewer than in the herring, there being 33 (T) in all. The lateral 

 processes of the vertebrae appear as far back as about the 23rd vertebra. 



My enumeration of the fin rays corresponds with Giinther's and Day's, 

 viz., D 19, P 16-17, V 9, A 23, C 19. In the shoulder girdle the 

 coracoid is much less perforated than the herring's, the scapula forms by 

 a ventral process about two-thirds of the scapular foramen, and the 1st 

 (dorsal) ray of the pectoral fin is relatively much stronger, less segmented, 

 and its inner half articulates with the scapula by a relatively stronger 

 head than occurs with the herring's. 



The bones of the skull are relatively stronger than those of the herring, 

 with apparently a corresponding reduction in the amount of cartilage 

 present. 



The posterior end of the skull is rather narrower. The supraoccipital 

 spine is, though still small, sharper and more pronounced than the 

 herring's, and the perforation for the posterior semicircular canal is 

 complete. The posterior projection or elbow of the epiotic has a sharper 

 termination, so as to form a distinct process, to which is attached a more 

 numerously divided muscular ossification than the simple bifurcated one of 

 the herring. Along the epiotic and exoccipital several others of these 

 spines are attached. The side of the cranium (pterotic and sphenotic 

 bones) is longer than the herring's. The anterior process of the sphenotic 

 is broader, and though sharp pointed, is less spike-like than the herring's ; 

 on the other hand, the posterior pterotic process is longer and more 

 slender. The aperture between the sphenotic and pterotic is relatively 

 wider and deeper. The under face of the skull formed by the exoccipitals, 

 opisthotic and prootic, is not so depressed, and therefore the auditory 

 fenestra faces slightly more outwards. The prootics meet in the middle 

 ventral line by a deep interlocking suture, so that when separated the 

 internal edge of each has a comb-like appearance. 

 2 0 



