170 NOTES ON THE SALMO SALAR SPECIMEN—MORROW. 
59-;. To this vertebral centrum is attached the lower hypural 
bone, which has a somewhat narrow neck, caused by a foramen 
on its anterior edge, which passes between it and the ray on the 
58th centrum, and a double foramen passing between the pos- 
terior edge of this hypural bone and the anterior edge of the 
second ; this double foramen appears to be for the passage of 
vessels uniting the (pulsating?) sacks. Also attached to this 
centrum is the second hypural bone; it is notched on its ventral 
anterior surface by the foramen above mentioned, the division 
of which is nearly parallel with the centrum; this division is 
caused by a slight projection in the centre of the foramen on 
this, as well as on the bone already described. At the posterior 
extremities the adjacent faces of the above two bones are partially 
rounded, that is, their adjoining corners are rounded off, and in 
the hollow thus formed, which is slightly above a line drawn 
through the centre of the spinal column, is a nervous corpuscle, so 
shrunken in this skeleton as now to be scarcely observed, hut when 
fresh, it measured three sixteenths of an inch in diameter. This 
corpuscle projects slightly beyond the edge of the hypural bones. 
60.. Attached to the ventral surface of a spongy centrum is the 
third hypural bone, and to its end, if indeed it does not belong 
to it, is attached the fourth hypural bone, terminating the sixty 
centra of the spinal column. We have therefore four hypural 
bones, which being strongly connected together as well as to the 
posterior ventral rays, form a broad solid plate for the attach- 
ment of the muscles, and the strengthening of the rays of the 
caudal fin. The bone lying next above this is the larger Y shap- 
ed bone, the notochord passes between the forks of this bone as in 
the smaller bone of similar shape. 
Prof. Huxley’s drawing, representing the tail of the Salmo 
published in his “Manual of the Anatomy .of Vertebrated 
Animals,” page 20, is incorrect if the Salmo of England are 
the same as ours. He makes the vertebral column in this 
drawing to end in a line common to the anterior vertebra, and 
at the end of the last centrum which is drawn of greater 
diameter than those which precede it, is attached at an angle 
nearly equal to that formed by the posterior part of the spina] 
column in the skeleton before you, a terminating bony plate, 
