g38 APPENDIX 



intermediate between iiilobites and the Arachnomorpha. Since they have antennae 

 they should probably be placed as a class in the subphylum containing the class Tnlo- 

 bita. 



PHYLUM 17. PHORONIDA. VVith a lophophore. No skeleton. One order. 



PHYLUM 18. BRACHIOPODA. With a lophophore. Dorsal and ventral shells. 



CLASS 1. INARTICULATA. Shells without hinge, anus present. Two orders. 



Lingula. 

 CLASS 2. ARTICULATA. Shells hinged, anus absent. Two or three orders. Lamp- 

 shells. 



PHYLUM 19. BRYOZOA. Moss animals. With a lophophore surrounding the mouth. 

 Circulatory system and nephridia absent. Two orders. Bugula. 



PHYLUM 20. CHAETOGNATHA. Arrow worms. Enterocoelous, with lateral fins. One 

 order. 



I 



PHYLUM 21. ECHINODERMATA. Deuterostomes with subepidermal calcareous plates 

 and usually radial symmetry on a plan of five. 



Subphylum 1. Pelmatozoa. Attached in youth or throughout life by an aboral stem, 

 t CLASS 1. HETEROSTELEA. Bilaterally symmetrical, possibly ancestral to others, 

 t CLASSES 2-4. CYSTIDEA, BLASTOIDEA, EDRIOASTEROIDEA. Radial symmetry, no 

 arms. 

 CLASS 5. CRINOIDEA. Sea lilies and sea feathers. Well developed arms, anus on 

 oral surface. One living and three extinct orders. 

 Subphylum 2. Eleutherozoa. Stemless unattached echinoderms. 



CLASS 1. HOLOTHURO.DEA. Sea cucumbers. Armless, elongate, with secondary 

 bilateral symmetry, skeleton reduced to microscopic spicules. 

 Five orders, all living. 

 CLASS 2. ECHINOIDEA. Sea urchins, sand dollars. Armless, skeleton well de- 

 veloped and usually rigid with numerous mobile spines. About 

 three living and five more extinct orders. 

 CLASS 3. ASTEROIDEA. Starfishes. With arms, skeleton well developed but flex- 

 il:)le, locomotion by tube feet. Three living and two more extinct 

 orders. Asterias, Leptasterias. 

 CLASS 4. OPHIUROIDEA. Brittle stars. With arms and flexible skeleton, loco- 

 motion by prehension. Two orders, both living, 

 t CLASS 5. OPHIOCISTIOIDEA. Armless. Body heavily armored, with a few pairs 

 of very large scaly tube feet. One extinct order. 



PHYLUM 22. HEMICHORDATA. Deuterostomes with bilateral symmetry, stomochord, and 

 usually with gill slits. 

 CLASS 1. ENTEROPNEUSTA. .\corn worms. Burrowing, wormlike animals with 



numerous gill slits. One order. Snccoglossiis. 

 CLASS 2. PTEROBRANCHIA. Sedentary animals with a dorsal anus, collar ex- 

 panded as a lophophore around mouth. 

 Order 1. Rhabdopleuridea. No gill slits, lophophore of two branching 



arms. 

 Order 2. Cephalodiscoidea. One pair of gill slits, lophophore of sev- 

 eral branching arms. 



