NOTES ON THE SALMO SALAR SPECIMEN — MORROW. 165 



The next bone we meet has its anterior edge divided, that is 

 it is Y shaped, so as to admit between its points the passage 

 of the notochord, together with its protecting tissues, and the 

 posterior edges of the saddle bones nearly touch the points of 

 this bone. Its posterior or outer edge is united, but in a younger 

 specimen would probably be found as two separate bones. This 

 bone is of the same shape, but about half the size of the Y shaped 

 bone to be noticed in the ventral aspect of the spinal column. 



I have thus reached the dorsal extremity of the spinal column, 

 not including the spongy centrum to which the fourth or upper hy- 

 pural bone is attached, and which makes, if included, 60 vertebrae. 



Spinal Column, Ventral aspect — Ribs. 



G 1 & 2. There are no ribs on the 1st and 2nd centra, these being 

 so situate as not to require them, but there are their representa- 

 tives in the shape of processes. 



1st pair on 3rd. From the 3rd centrum, at its lower edge 

 spring the first pair of ribs, which are somewhat crooked in 

 shape, and naturally shorter than the others. They are com- 

 paratively round bones, and in length from articulation to point 

 2 inches. 



G. 4- The second pair of ribs, measured in a direct line, that is 

 not following their curve, are 2f inches in length arid slightly 

 deeper measured transversely than they are laterally/and taper 

 to a point. 



G. 5. The third pair are 3£ inches long. 

 G. 6. The fourth pair are 3f inches long. 



It is not necessary to give the lengths of the remainder of the 

 ribs, but it may be remarked that I find in the Salmon, that the 

 first two pair of ribs may be termed short, and that from 

 and including the 3rd pair, to and including the 13th pair, they 

 are of much greater transverse than longitudinal diameter, de- 

 creasing in the length of the transverse breadth as they succeed 

 each other posteriorly — 7 to 12 are the longest and broadest ribs. 

 The remaining ribs are widest at their attachment and gradually 

 decrease in size towards their points. 

 C. #7. At the 25th pair of ribs on the 27th centrum are a pair of 



