Organization of the lophophore in Lingula anatina.

(A) Overview of a live L. anatina. (B) The central portion of the lophophore. The mouth (m) is covered by the brachial fold (bf). (C) A portion of the brachium, dorsal side; SEM. (D) Cross section of two rows of tentacles and the brachial fold (bf); SEM. (E) A portion of the brachium, ventral side; SEM. (F) Small stabs (ss) between outer tentacles. Abbreviations: ba, base of the brachium; bf, brachial fold; it, inner tentacles; m, mouth; ot, outer tentacles; pe, peduncle; s, setae; sh, shell; ss, small stubs.