CLASSIFICATION 225 



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 : Eattulm E., Mastigocerca K, Coelopus G., Diurdla (?) 



Eyfurth. 



Fain. 1 6. Dinocharididae : Dinocharis E., Scaridium E., Stephanops E. 

 Fam. 17. Salpinidae : Salpina E., Diaschiza G., Ploesoma Herrick, Diplax 



G., Diplois G. 



Fam. 18. Euchlanididae : Euchlanis E., Dapidia G., Apodoides Joseph. 

 Fam. 19. Cathypnidae : Cathypna G., Distyla Eckstein, Monostyla E. 

 Fam. 20. Coluridae : Colurus E., Metopidia E., Monura E., Mytilia G., 



Cochleare G., Dispinthera, G. 



Fam. 21. Pterodinidae : Pterodina E., Pompholyx G. 

 Fam. 22. Brachionidae : Brachionus E., Noteus E., Schizocerca Daday. 

 Fam. 23. Anuraeidae : Anuraea E., Notholca G., Eretmia G. 



The group includes a number of very minute forms, besides 

 others conspicuous both for size and beauty. A soft dorsal flap 

 above the head occurs in Stephanops ; also in Coluridae, a large 

 family of minute species, where the flap is movable, and looks 

 in profile like a hook overhanging the forehead. The genus 

 Pterodina, like Pedalion and Triarthra, combines a Bdelloid disc 

 with malleoramate trophi, while its exsertile wrinkled foot ends 

 in a ciliated cup like that of a larval tubicolous species. 



Brachionus, a large, often flat, transparent form, with a long 

 wrinkled foot, is a very common genus, known to the earlier 

 observers, and repeatedly figured by them. Pompholyx has a sack- 

 like lorica, no foot, and carries its immense egg suspended by an 

 elastic thread from the cloaca. The Anuraeidae lack the foot, 

 and often have great spines or bristles projecting from the lorica, 

 which no doubt facilitate floating. They are abundant in the 

 "plankton " or floating fauna of large lakes far from the shore. 

 Many marine species belong to this family. 



Order VII. Seisonaceae. Marine Rotifers parasitic on the 

 Crustacean Nebalia ; males resembling the females. Body 

 elongated, with a slender retractile neck, a much reduced disc, an 

 elongated foot with a terminal perforated disc as in Callidina. 

 Trophi virgate exsertile. Geni to-urinary cloaca opening at the 

 base of the neck in the male, at the hinder end of the body in 

 the female. Intestine complete (Seison) or blind (Paraseison}. 1 



1 For a full account of this group see Glaus in Festschr. Z.-B. Ges. Wien, 1876, 

 p. 75 ; and Plate vi Mt. Stat. Neapel, vol. vii. 1886-87, p. 234 ; Ann. A'at. Hist. 

 ser. 6, vol. ii., 1888, p. 86. 



VOL. II Q 



