The Cristatellina consist of a single genus and probably of a single species (_Cristatella mucedo_, Cuvier), which is widely distributed in Europe and N. America, but has not been found in the Oriental Region. Eight genera of Plumatellina are known, and five (possibly six) of these genera occur in India. Division PLUMATELLINA, nov. The structure of the species included in this division is very uniform as regards the internal organs (see fig. 40 opposite and fig. 47 _a_, p. 236). The alimentary canal is simpler than that of the Paludicellidæ. A short oesophagus leads directly into the stomach, the cardiac portion of which is produced as a vertical limb almost cylindrical in form and not constricted at the base. This limb is as a rule of greater length than the oesophagus. The pyloric part of the stomach is elongated and narrow, and the intestine short, straight, and of ovoid form. There are no cilia at the pyloric opening. A single funiculus joins the posterior end of the stomach to the wall of the zooecium, bearing the statoblasts. Sexual organs are often absent. [Illustration: Fig. 40.--Structure of the Plumatellina (after Allman). A=a zooecium of _Fredericella_ with the polypide extruded. B=the lophophore of _Lophopus_ (tentacles removed) as seen obliquely from the right side. C=larva of _Plumatella_ as seen in optical section. _a_=tentacles; _b_=velum; _c_=epistome; _d_=mouth; _e_=oesophagus; _f_=stomach; _g_=intestine; _h_=anus; _j_=retractor muscle; _k_=parieto-vaginal muscles; _l_=funiculus.] Two families may be recognized as constituting the division, _viz._, (_a_) the Fredericellidæ, which have a circular or oval lophophore and simple statoblast without a swim-ring, and (_b_) the Plumatellidæ, in which the lophophore is shaped like a horseshoe and some or all of the statoblasts are provided with a ring of air-spaces. Family 1. FREDERICELLIDÆ. FREDERICELLIDÆ, Kraepelin, Deutsch. Süsswasserbryozoen, i, p. 168 (1887). _Zoaria_ dendritic; _zooecia_ distinctly tubular, with the ectocyst well developed; _statoblasts_ of one kind only, each surrounded by a chitinous ring devoid of air-spaces; _polypides_ with the lophophore circular or oval when expanded. The Fredericellidæ consist of a single genus (_Fredericella_) which includes several closely-allied forms and has a wide geographical distribution. Genus FREDERICELLA, _Gervais_ (1838). _Fredericella_, Allman, Mon. Fresh-Water Polyzoa, p. 11 (1857). _Plumatella_, ("arrêt de développement") Jullien, Bull. Soc. zool. France, x, p. 121 (1885). _Fredericella_, Kraepelin, Deutsch. Süsswasserbryozoen, i, p. 99 (1887). _Fredericella_, Goddard, Proc. Linn. Soc. N. S. Wales, xxxiv, p. 489 (1909).