THE ANIMAL KINGDOM 



413 



stomach, and intestine. An anal opening may or may not be 

 present. There is a circulatory system consisting of a heart, 

 blood vessels, and lacunar spaces. The body cavity is repre- 

 sented by a space in each mantle, connected with the cavities of 

 the lophophores. Nephridial tubes, one or two pairs, connect 

 the body cavity with the space between the two mantles. Usually 

 dioecious, there is a trochophore larval stage resembling a similar 

 stage in annelids (p. 415). Like bryozoans, brachiopods are very 

 ancient animals, of which fossils are known from the Cambrian to 



Lophophore 

 Dorsal valve 



Gonad 



Digest i ve gland 



Sfomacb 



Heart 



Venfra/ 



Manile 

 Fig. 240. — Semidiagrammatic sagittal section of a brachiopod, Magellania 

 lenticularis. (From Van Cleave, Invertebrate Zoology, after Parker and Haswell.) 



the present time. According to Pratt, there are about 2,500 

 fossil species and about 120 living species known at the present 

 time. 



Examples: Terebratulina septentrionalis, off Cape Cod; 

 Laqueus calif ornicus, California coast. 



PHYLUM 11— PHORONIDEA 



The Phoronidea are a small group of animals of uncertain 

 systematic position but showing some resemblance to bryozoans 

 and brachiopods. They are marine worms living in chitinous 

 tubes within which the body can be completely withdrawn. A 

 lophophore, consisting of a horseshoe-shaped ridge, bearing ten- 

 tacles, is present at the anterior end of the body and can be thrust 

 out of the tubes. The tubes frequently form tangled masses but 

 do not communicate with one another. Each animal develops 

 from a fertilized egg and there is no asexual generation formed by 

 budding. The mouth, located in the center of the lophophore, 



