KEY TO ANIMAL PHYLA 3 



17(14, 18) Worms with a cylindrical or filiform body with a thick 

 smooth outer covering. Anus usually present ; in water, 

 soil, or parasitic. Phylum Nemathelminthes, p. 14 



18(17, 14) Not wormlike, frequently covered by calcareous 

 horny or gelatinous secretion. If shell is absent, 

 animal with well-developed head. 19 



19(20, 21) Sessile animals, frequently in colonies which are covered 

 by homy or calcareous or gelatinous covering. Anus 

 present, near the anterior end of the body. A circle 

 or crown of ciliated tentacles about the mouth. Marine 

 and fresh water. Phylum Bryozoa, p. 16 



20(19, 21) Sessile, solitary, marine, mollusk-like animals; the body 

 inclosed in a bivalve, asymmetrical, horny or calcareous 

 shell, one valve of which is dorsal, the other ventral; 

 hinged at posterior end; usually attached by a muscu- 

 lar peduncle which protrudes near the hinge. Ten- 

 tacular arms prominent within the shell. (Pratt 264.) 



Phylum Brachiopoda 



21(19, 20) Animals usually free moving (always so in fresh 

 water), either bilaterally symmetrical or in part spirally 

 coiled. A fold of the body wall, the mantle, usually 

 present and inclosing the body. A calcareous shell 

 consisting of one (snails), two (clams and mussels), 

 and rarely of several pieces (marine). This normally 

 incloses the body but may be reduced to a thin dorsal 

 plate, invisible externally (marine) or entirely absent. 

 In last two cases (as in slugs) , the head is well developed. 

 The ventral surface is almost always provided with a 

 locomotor organ, the foot, which may be used for 

 creeping, swimming, or attachment. Animals rarely 

 parasitic. Phylum Mollusca, p. 18 



22(13) Body divided into segments as indicated by con- 

 strictions on the surface, by the number and arrange- 

 ment of bristles or appendages or by the arrangement 

 of internal organs. 23 



