180 



ZOOJ.OGY 



(Fig. 169). Some of the fresh-water forms make loose, antler- 

 hke colonies (Fig. 170), while others lie on the surface of a 

 more or less spherical mass of jelly which they have themselves 

 secreted. 



The lamp-shells (Brachiopoda) are a vanishing class. Their 

 fossil remains crowd the rocks almost from the first appearance 



of organic remains. While 

 thousands of fossil species 

 have been described, only 

 about 125 li\'ing species 

 are known, — all marine. 

 Although the individuals 

 are usually numerous in 

 localities where they occur, 

 the localities are few. In 

 our country they are found 

 on the coast of Alaine and 

 Fig. 172. — The brarhiopod Magr-iiania, near Cape Hatteras. The 



with the ventral valve removed, c;), the .p, ,. i v 



"cardinal" projection of shell; \p)u the 1-SrachlopOda have a tWO- 



bearer of the tentacles " lophophoie " ; yglyed shell like a clam, 



Iph, its coiled ami, the tentacles removed 



from right side ; mlh, mouth. From Par- but the valves are not 



ker and Haswell. ^j^j^^ ^^^_^ jp^^_ ,^^^ ^j^^^^j 



and ventral (Fig. 171), and consequently have nothing to do 

 with the shells of mollusks. The body somewltat resembles 

 that of a single iitdividual of a Bryozoan colony — two arms 

 stand \x\) on the right and l(>ft of the mouth and these are 

 crowded with tentacles whose cilia create a vortex in the water, 

 bringing small particles to the mouth (Fig. 172). The food 

 canal is bent like a U, the loop of the U being at the hinge of 

 the valves, half buried in the sand, while mouth and arms are 

 elevated into the surrounding water. On account of the fact 



