NOTES ON THE SALMO SALAR SPECIMEN — MORROW. 171 



and to the ventral edge of this are attached two hypural bones. 

 There are also some other bones which do not correspond to some 

 in our salmo. On page 131 of the same work he says " the spinal 

 " column appearing to terminate in the centre of a wedge-shaped 

 " hypural bone, to the free edges of which the caudal fin rays are 

 " attached, so as to form an upper and a lower lobe, which are 

 " equal or sub-equal. This characteristically Teleostean structure 

 " of the tail-fin has been termed homocercal — a name which may 

 " be retained, though it originated in a misconception of the re- 

 " lation of this structure to the heterocercal condition.'' 



The caudal fin-rays in my specimen are not attached to the 

 " free edges of the hypural bones," but their divided ends overlap 

 the hypural bones on each side ; on the dorsal part about five- 

 eighths of an inch ; a quarter of an inch on the central, and from 

 a quarter to half an inch on the inferior or ventral part. In the 

 drawing referred to one of the fin-rays is inserted in a notch in 

 the posterior edge of the upper hypural bone, nearly in the place 

 where the corpuscle already mentioned should be. 



Transverse Processes. 



The transverse processes are attached directly to the centra, 

 and begin on the 1st centrum. The first four are nearly at right 

 angles to the column, and project posteriorly into the fleshy 



tissue, and are say I4, \\, 1, U inches in length, from 4 to 25, 

 their outer extremities rising gradually towards the dorsal line. 

 They are of variable length, 1 to 1^ inches, not gradually decreas- 

 ing, but some long, others shorter — including 26 to 32, they rise 

 rapidly towards the dorsal line, so that their dorsal ends are near 

 to the spinous rays ; all the transverse processes arise from their 

 centra posterior to their corresponding ray. Besides the trans- 

 verse processes enumerated, which are bony, there are some 

 that appear to be attached by tissue to their centra, having 

 soft bony extremities; these have their attachment gradually 

 rising on the dorsal spinous rays, but soon they lose their bony 

 texture, and appear only as threads attached to the muscular 

 tissue. 



