Sabur, a conspicuous mass in the extreme south, is 9900 ft., with a fall to the Taiz valley of 5000 ft.; farther north several points in the mountains above Ibb and Yarim attain a height of 10,500 ft., and J.
A circlet of radially situate infrabasals (IBB) may also be present.
- Crinoidea in which the base consists of BB and IBB, the latter being liable to atrophy or fusion with the proximale, but the aboral prolongations of the chambered organ are always radial; new columnals may or may not be introduced at the proximal end of the stem.
Top columnal a persistent proximale, often fusing with IBB, which are frequently atrophied in the adult.
IBB always the primitive 5.
How would you define IBB? Add your definition here.