204 INVERTEBRATE ZOOLOGY 
PHYLUM VII. ECHINODERMATA 
Radially symmetrical animals with calcareous plates or spicules in 
the body-wall. 
Class 1. Crinoidea. Sea lilies. Echinoderms which are sessile 
throughout life or only as larve. Ex. Comatula. 
Class 2. Asteroidea. Starfish. Flattened, star-shaped echino- 
derms with an ambulacral furrow on the under side of each ray. 
Ex. Asterias. 
Class 3. Ophiuroidea. Brittle stars. Flattened echinoderms with 
long, vibratile arms and without ambulacral furrows. Ex. Amphiura. 
Class 4. Echinoidea. Sea urchins. Spheroidal or flattened echino- 
derms without arms. Ex. Arbacia. 
Class 5. Holothurioidea. Sea cucumbers. More or less worm-like 
echinoderms with oral tentacles. Ex. Synapta. 
PHYLUM VIII. CHORDATA 
Animals with a dorsal central nervous system, an internal skeletal 
system, consisting in the simplest cases of the notochord, and paired 
pharyngeal slits and arches. 
Suppyyium I. Enteropneusta. Worm-like chordates with a large 
proboscis in front of the mouth. Ex. Balanoglossus. 
SuppHyivum II. Tunicata. Chordates in which the body is enclosed 
in a tunic; a large pharyngeal chamber and a ventral heart present. 
Class 1. Larvacea. Minute, free-swimming tunicates with a long 
tail. Ex. Appendicularia. 
Class 2. Thaliacea. Free-swimming, transparent tunicates. Ex. 
Salpa. 
Class 3. Ascidiacea. Sessile, saccular tunicates, either simple or 
colonial. Ex. Molgula. 
Suspuyium III. Leptocardia. Elongated, fish-like chordates, com- 
pressed laterally and attenuated at both ends. Ex. Amphioxus. 
SuppyyLtum IV. Vertebrata. Chordates with distinct head, bear- 
ing organs of special sense, with red blood, and usually with two 
pairs of appendages. 
Class 1. Pisces. Fishes. Aquatic vertebrates which breathe by means 
of gills, and usually with bony scales and paired fins, Ex, Perca. 
