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 larvse. 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. 



Subphylum I. Enteropneusta. Worm-like chordates with a large 

 proboscis in front of the mouth. Ex. Balanoglossus. 



Subphylum 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. 



Subphylum III. Leptocardia. Elongated, fish-like chordates, com- 

 pressed laterally and attenuated at both ends. Ex. Amphioxus. 



Subphylum 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. 



