INTRODUCTION, IQ. 
Order 3. Cystoidea (extinct). 
Order 4. Ophiuroidea (Brittle-stars).—Zx. Sand-stars (Ophiura), 
Brittle-stars (Ophiocoma). 
Order 5. Asteroidea (Star-fishes).— x. Cross-fish (Uraster), Sun- 
star (Solaster), Cushion-star (Goniaster). 
Order 6. Echinoidea (Sea-urchins). —Zx. Sea-eggs (Echinus), 
Heart-urchins (Spatangus). 
Order 7. Holothuroidea (Sea-cucumbers.—Zx. Trepangs (Holo- 
thuria). 
B. SCOLECIDA.—Body usually flattened, or cylindrical and worm- 
like ; integument soft, without lime. Water-vascular system not assist- 
ing in locomotion. Nervous system consisting of one or two ganglia or 
little masses, and not disposed in a radiate manner. 
Order 1. Zeniada.—Ex. ‘Tape-worm (Teenia). 
Order 2. ZTrematoda (Suctorial worms).—Zx. Liver-fluke (Dis- 
toma). 
Order 3. Zurbellaria. — Hx. fPlanarians (Planaria), Ribbon- 
worms (Nemertes). 
Order 4. Acanthocephala (Thorn-headed worms).—Zx. Echino- 
rhynchus. 
Order 5. Gordiacea (Hair-worms).—Zx. Gordius. 
Order 6. Mematoda(Thread-worms).—Zx. Round-worm (Ascaris), 
Guinea-worm (Filaria), Vinegar-eel (Anguillula). 
Order 7. Rofifera (Wheel-animalcules).—Zx. Builder-animalcule 
(Melicerta), Flexible Creeper (Notommata). 
SuB-KINGDOM IV.—ANNULOSA. 
Animal composed of numerous definite segments or “‘somites,”’ ar- 
ranged longitudinally, one behind the other. Nervous system always 
present, consisting of a double chain of nervous masses, or ganglia, 
which are placed along the lower surface of the body, and form a collar 
around the gullet. Limbs (when present) turned toward that side of the 
body on which the main masses of the nervous system are situated. 
Division A. ANARTHROPODA. — Locomotive appendages, when 
present, not distinctly jointed or articulated to the body. 
Cuass I. GEPHYREA.—£x. Spoon-worms (Sipunculus). 
Cuiass IJ. ANNELIDA (Ringed-worms). 
Order 1. Hirudinea.—L£x. Leeches (Sanguisuga, Hirudo). 
Order 2. Oligocheta. — Ex. Farth-worms (Lumbricus), Water- 
worms (Nais). 
Order 3. Zubicola.—Ex. Tube-worms (Serpula). 
Order 4. Errantia. — Ex. Sand-worms and_ Sea- centipedes 
(Nereis), Lob-worm (Arenicola), Sea-mouse (Aphrodite). 
Crass III. CH@TOGNATHA (Arrow-worms).—£x. Sagitta. 
Division B. ARTHROPODA.—Locomotive appendages jointed or 
articulated to the body. 
