The zooids are a modification of the type of structure known in Balanhglossus, from which they differ principally in the following respects: (i.) The alimentary canal, instead of being straight, has a U-shaped flexure, the dorsal line between the mouth and the anus being short.
In New Mexico, if glaciers were formed at all in the high valleys, they were so small as not greatly to modify the more normal forms. In central Colorado and Wyoming, where the mountains are higher and the Pleistocene glaciers were larger, the valley heads were hollowed out in well-formed cirques, often holding small lakes; and the mountain valleys were enlarged into U-shaped troughs as far down as the ice reached, with hanging lateral valleys oii the way.
Some of the western valleys have also in part of their length beeIi converted into U-shaped troughs; the famous Yosemite Vailey, eroded in massive granite, with side cliffs 1000 or 2000 ft.
Like the Lewis and Clark range, its crest is broken by numerous U-shaped wind-gaps and its west slope is cut by glacial troughs containing long narrow lake basins.
Phioxus; (c) the skeletal rods in the tongue-bars of Balanoglossus are double; (d) the tongue-bar in Balanoglossus does not fuse with the ventral border of the cleft, but ends freely below, thus producing a continuous U-shaped cleft.
The U-shaped electrolytic vessel and the electrodes are made of an alloy of platinum-iridium, the limbs of the tube being closed by stoppers made of fluor-spar, and fitted with two lateral exit tubes for carrying off the gases evolved.
They may be defined as aquatic animals, forming colonies by budding; with ciliated retractile tentacles and a U-shaped alimentary canal.