386 ZOOLOGY 



ECHINODERMATA 



Animals of a prevailingly radial structure, with intestinal wall dis- 

 tinct from body-wall and with calcareous plates in the skin (192). 



CR1NOIDEA. Sessile Echinodermata, having a cup-shaped body 

 (203). 



ASTEROIDEA. Star-shaped Echinodermata, with a furrow along 

 the under side of the arms (193). 



OPHIUROIDEA. Star-shaped Echinodermata, with ungrooved 

 arms (198). 



ECHINOIDEA. With armless, globular, or cake-shaped body (199). 



HOLOTHUROIDEA. Worm-like, with tentacles around mouth 

 (201). 



ANNELIDA 



Bilateral, segmented worms without jointed legs. 



POLYCH.3STA. Annelida possessing parapodia on one or more 

 segments, and with many bristles on parapodia. ERRANTIA, free- 

 swimming Polychaeta: Autolytus (147), Lepidonotus (147), Xe- 

 reis (145), Euglycera (147). SEDKNTARIA, Polychaeta which live in 

 tubes composed of mud, sand, or lime: Cirratulus (149), Amphi- 

 trite (150), Polycirrus (150), Cistenides (151), Clymenella (150), 

 Serpula (151). 



OLIGOCH^ETA. Annelida without parapodia and with few setae ; 

 living in fresh water or in the ground. LIMICOL^:, aquatic : Nais 

 (137); Dero (137); Tubifex (136). TERRICOL*:, earth-inhabiting: 

 Allolobophora, Lumbricus (133). 



GEPHYREA. Annelida having sessile habits and consequently 

 without external segmentation in the adult, setae sometimes present. 

 Phascolosoma (139), Echiurus (139). 



HIRUDINEA. Annelida with short rings or none at all and with 

 a ventral sucker ; "bloodsuckers." Clepsine (141) ; Nephelis (140). 



ARTHROPODA 



Symmetrical, segmented animals, with jointed appendages. 

 CRUSTACEA. Typically, aquatic and gill-bearing Arthropoda. 

 Two pairs of antennae, except in Gigantostraca. 



