Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 115 



against a slight depression on the anterior edge of the next poste- 

 rior vertebra, immediately ventral to the anterior process of that 

 vertebra. 



On the lateral surface of the first vertebra, immediately poste- 

 rior to the anterior edge of the spreading base of the spine-like 

 portion of its dorsal arch, there is a deep depression, which re- 

 ceives and gives articulation to the proximal end of the associated 

 horizontal rib. The foramen for the ventral root of the associated 

 spinal nerve lies immediately posterior to this depression, in an- 

 other, smaller but often even deeper depression. On the second 

 vertebra the depression that lodges the articular end of the asso- 

 ciated horizontal rib lies in the spreading base of the spine of the 

 arch, the foramen for the ventral root of the associated nerve lying 

 in a depression immediately posterior to the base of the spine. 

 The next four vertebrje resemble the second excepting that there 

 is, immediately anterior to the depression at the base of the spine 

 of each vertebra, a second, but only slightly marked, depression. 

 On all of these latter vertebras the large depression lodges the 

 proximal end of the ventral rib of the vertebra, and not that of the 

 horizontal one, as it does on the first two vertebrae. The small 

 anterior depression lodges the articular end of the horizontal rib. 



On the first and second vertebrae there were, in all the specimens 

 examined excepting one, but a single rib, the horizontal rib, on 

 each side. The articular ends of these ribs are enlarged, and each 

 fits into and fills the articular depression on the vertebra with 

 which it articulates. On all the other vertebrae examined there 

 were two ribs on each side, a horizontal one and a ventral one. 

 The articular end of the ventral rib was enlarged and articulated 

 with its vertebra in the large posterior articular depression. The 

 articular end of the horizontal rib was reduced to a flat line and 

 articulated with the vertebra in the shallow, anterior articular de- 

 pression. The flat articular end of the horizontal rib, on these 

 vertebrae, lies against the anterior surface of the corresponding 

 ventral rib, the articular ends of the horizontal ribs on the poste- 

 rior vertebrae lying relatively more ventral than on the anterior 

 ones. On the second vertebra of one specimen there was a short 

 ventral rib on each side, the rib being only one third or one quar- 

 ter as long as the next following ventral rib. 



