Cyclostomata

Cyclostomata (round-mouths). 1. A class of Vertebrates having no true jaws or limbs. Examples are the Hag-fish and the Lamprey, both which see. 2. A sub-order of Bryozoa (q.v.), in which the colony has a calcareous skeleton (zoarium) composed of long tubes. These open by a terminal orifice which is the same size as the tubes. They are the simplest of the three principal sub-orders of living Bryozoa, but are now less important than they once were. The English species only number a little over 30, though they were more abundant in the Chalk and Oolitic seas. The Crisiidae and Tubuliporidae are the two principal living English families, but representatives of them are rare in comparison with the Cheilostomata.