of the Fishery Board for Scotland. 



267 



dages (or dorsal intermusculars as, posterior to this point, they must now 

 be called), run much backwards here and near the outer surface of the 

 myotomes, just as do the corresponding ventral intermusculars. Where they 

 become detached from the neural spine (22nd vertebra), these bones show 

 a slightly thickened portion at about 3 mm. or 4 mm. from their base, 

 which gives attachment to a short connective tissue thread. This latter 

 ossifies further back as a branch of these bones, growing longer posteriorly, 

 that of the 25th vertebra being quite a short process. 



The branch is given off from the outer anterior face of the main stem, and 

 runs nearest the surface. It gives attachment along its length externally 

 and internally to the sheet of connective tissue surrounding the myotomes. 



Going further back, we find the position and attachment of the proximal 

 portion of the bone being shifted further and further in an upward direction 

 from the vertebral column, and along the neural spines, so that about the 

 30th vertebra it springs from near the tip of the neural spine, and is attached 

 to it. In consequence of this the curvature of the bone gets greater, the 

 position of the bifurcation gets nearer and nearer its tip, and eventually 

 the proximal part looks like a branch given off from its own distal portion, 

 while the real branch already referred to, becoming gradually longer, comes 

 to lie in a directly continuous line with the distal portion, forming with 

 it the main intermuscular bone. The shortening inner process (original 

 head of bone), disappears at the position of the 47th or 48th vertebra, and 

 the bones lie side by side longitudinally along the posterior caudal portion 

 of the herring, terminating with that corresponding to the 54th vertebra, 

 and which in the 292 mm. long fish is about 12 mm. in length. These 

 dorsal intermusculars are in fact similar in almost every respect to the 

 posterior intermusculars ventral to the vertebral column. But there are 

 no dorsally situated bones corresponding exactly either in form or position 

 to the anterior ventral intermusculars, although the neural arch lateral 

 appendages partially fill their place. 



It has been stated that the 1st vertebra is provided with a neural arch 

 and its lateral appendage. In front of this, however, come a couple of 

 bones, lying between the anterior myotomes there. One of these slender 

 bones is provided with a short branch, springing from its head and pro- 

 jecting upwards and backwards, and the whole lies in front of and above 

 the first vertebral neural arch. Its form is exactly that of a neural arch 

 and its appendage, and it belongs to what may be called a prevertebral 

 myotome. In front of, in actual position dorsal to, this bone come 

 one or two long and slender bones, having their single, slightly thickened, 

 heads fixed close to the epiotic bone of the cranium, and their backward 

 projecting terminal portions broken up into two or three delicate bones 

 or branches, which lie close together. These seem to be ossifications of 

 the ligaments attaching some of the dorsal muscles. 



The Vertebra and Arches of the Tail. 



It has already been stated, that while the vertebrae may vary in number 

 in the herring from 56 to 58, the usual numbers are 56 and 57, the more 

 common being 57. It must be understood, however, what this means. 

 In the adult herring the last fairly visible vertebra is not so complete in 

 its form as are the others ; whereas its anterior end is of the usual form, 

 and articulates in almost the normal manner wi,th the previous vertebra, 

 its posterior end is so contracted in size, the vertebra appearing to end 

 just at its centre and therefore without the usual posterior expansion, 

 as generally to be scarcely noticed. The numbers of vertebrae given above 



