Fam. 10. Hydatinidae: Hydatina E. (Fig. 106), Notops H., Hudsonella Zach., Cyrtonia Rouss.
Fam. 11. Synchaetidae: Synchaeta E.
Fam. 12. Notommatidae: Notommata E., Pleurotrocha E., Copeus G., Proales G., Furcularia G., Eosphora G., Triophthalmus E., Diglena E. (Fig. 113), Distemma E., Triphylus E., Taphrocampa G., Albertia Duj., Balatro Clap.
Fam. 13. Drilophagidae: Drilophagus Vejdovsky.
Fam. 14. Triarthridae: Triarthra E., Polyarthra E., Pteroessa G., Pedetes G.
Fig. 117.—Pedalion mirum, female. (After Hudson.) A, Ventral view; B, side view. a, Median antenna; al, antero-lateral limb; an, anus; ci, cingulum; dl, dorso-median limb; e, eye; f, ciliated pedal processes; l, lip; m, mouth; pl, postero-lateral limb; tr, trochus; vl, ventro-median limb.
To this group belongs the eyeless Hydatina, a classical object of study, common in greenish pools, whose male was the first male Rotifer to be figured by Ehrenberg (1838), though he did not recognise its nature, and gave it the name of Enteroploea hydatina. Rhinops has the back of the corona curiously prolonged forwards into a sort of proboscis bearing two eyes. Some species of Notommata and Proales are distinctly annulated; in Taphrocampa the segmentation is so marked as to give the appearance of mesenteric septa extending inwards from the body-wall to the intestine. Microcodon has a wreath which is very peculiar in its extreme simplicity, with the mouth nearly central, and the eye lying just dorsal to the mouth. The Triarthridae, which resemble the Scirtopoda in having strong leaping spines fringed by fine bristles, should perhaps be placed in the next sub-Order.
Sub-Order B. Loricata.—Ploima with a firm elastic cuticle of definite form, persistent after death, continuous, or divided by thinner strips into plates or shields, which again may be areolated. The cuticle may also be shagreened or embossed in various ways.
Fam. 15. Rattulidae: Rattulus E., Mastigocerca E., Coelopus G., Diurella (?) Eyfurth.