APPENDIX. 291 
Fig. 5.—Left of 5 is the small or superior Y shaped bone. 
Right of 4 is the larger or inferior Y shaped bone. 
Fig. 6.—Left of 6 is the short bone (one of a pair) page 164. 
Right of 6 is the bone e, plate 10, page 175.—[Figs. 5 and 6 are 
from same fish as plate 11.] 
In order to make plate 11 more clear, I have to add: 
The spinal chord (myelon) passes upon the dorsal aspect of the 
centra, covered by a very strong sheath, which lies between the 
ventral extremities of the dorsal spinous rays until it reaches the 
end of the vertebrve, it there divides into two principal filaments 
which are inclosed ina wire at the anteriér extremity o! the 
upper or small Y shaped bone. One of these filaments lies upon 
the notochord, following it to its extremity, where it becomes 
minutely divided and lost in the general structure. The second 
or posterior dorsal wire, incloses the notochordal branch ; the other 
T have not attempted to follow. 
The notochord passes from the posterior edge of the spongy 
centrum (page 170) between the forks of two Y shaped bones, 
lying upon the upper edge of the superior and shorter one, and 
extends following the curve of the dorsal long fin ray at its 
superior edge, being overlapped by the longest of the short fin 
rays (in this specimen 2 inches in length) next to the long finray, 
a distance of 1 inches. The centre of the notochord being 
exactly half an inch from the dorsal edge of the caudal fin, where 
in plate 11 it is marked by a wire. The notochord where it 
issues from the forks of the superior Y shaped bone, in this 
specimen is nearly } of aninch in diameter, decreasing a little in 
size until near its extremity, where it is slightly enlarged and 
has a somewhat blunt rounded termination; it is jointed in 
structure or rather shows the divisions which in the body of 
the fish form the centra. 
The wire loop nearly in a line with the centre of the spinal 
column, plate 11, incloses the nervous corpuscle (page 170,) which 
receives filaments from a ganglion by a branch from the spinal 
chord. 
On the left side of the tail, plate 10, figure 4, is shown the 
orifices of the pulsating? sack (page 170); the outer part of the 
