The vertebrae are solid and may be opisthocoelous, biconcave, or flat.
The vertebræ of its backbone are not biconcave, but flat in front and behind.
Owing to the beaded structure of the notochord the vertebral bodies take of necessity a biconcave hourglass-shaped form.
The end result is an amphicoelous or biconcave centrum in general appearance much like that of the Selachian.
The human blood-corpuscle is a non-nucleated, biconcave disc, having a diameter of about 1/3500 of an inch.
It had also the curious and old-fashioned peculiarity of biconcave vertebræ, like those of fishes and some reptiles.
The vertebræ are very numerous and biconcave as in ordinary fishes.
Biconcave cartilaginous vertebrae are developed, and as is the case in most fishes, constrict the notochord vertebrally.
The vertebral centra are opisthocoelous or biconcave, and there are numerous precaudal vertebrae.
The vertebrae are biconcave and are very numerous; very few however belong to the tail.