The name Brachiopod (/3paxiwv, an arm, and hots, ir036s, a foot) was proposed for the class by F.
The soft body of the Brachiopod is in all cases protected by a shell composed of two distinct valves; these valves are always, except in cases of malformation, equal-sided, but not equivalved.
The valves are, consequently, essentially symmetrical, which is not the case with the Lamellibranchiata, - so much so, that certain Brachiopod shells were named Lampades, or lamp shells, by some early naturalists; but while such may bear a kind of resemblance to an antique Etruscan lamp, by far the larger number in no way resemble one.
The young Brachiopod in all its species is protected by an embryonic shell called the " protegulum," which sometimes persists in the umbones of the adult shells but is more usually worn off.
The body of the Brachiopod v usually occupies about the posterior half of the space within the shell.
The water which bears the oxygen for respiration and the minute organisms upon which the Brachiopod feeds is swept into the mantle cavity by the action of the cilia which cover the arms, and the eggs and excreta pass out into the same cavity.
Xliv.) has classified with appropriate names the various stages through which Brachiopod larvae pass.
The protegulum has been found in members of almost all the families of Brachiopod, and it is thought to occur throughout the group. It resembles the shell of the Cambrian .4 genus Iphidea [Paterina], and the Phylembryo is frequently referred to as the Paterina stage.
There is, however, a considerable amount of resemblance between the lophophore of Phoronis australis, with its spirally twisted ends, and that of a typical Brachiopod; nor do the structural details of the adult Brachiopods forbid the view that they may be related to Phoronis.
The brachiopod body, the 3.