DISTRIBUTION OF BRACHIOPODS. 195 



having some molluscan features, such as a solid shell, though 

 having nothing homologous with the foot, the sheil-gland 

 or odontophore of mollusks. 



In accordance with the fact that the Brachiopods are a 

 generalized type of worms, the species have a high antiquity, 

 and the type is remarkably persistent. The Lingula of our 

 shores {L. pyramidata Stimpson, Fig. 134) lives buried in 

 the sand, where it forms tubes of sand around the peduncle, 

 just below low- 

 water mark from 

 Chesapeake Bay, 

 to Florida. It has 



remarkable vital- ^*'*7^^ 4 If /^^ ^ 



ity, not only with- (I^S ^^/ A 'J 



standing the 

 changes of tem- 

 perature and ex- 

 posure to death 



from various oth- I'ig' Wi.—Ungula pyramidata making sand-tubes ; 

 natural size. — After Morse. 



er causes, but will 



bear transportation to other countries in sea- water that has 

 been unchanged. Living Lingulse have been carried by Prof. 

 Morse from Japan to Boston, Mass., the water in the small 

 glass jar containing the specimens having been changed but 

 twice in four months. The living species of this cosmopol- 

 itan genus differ but slightly from those occurring in the 

 lowest fossiliferous strata. Between eighty and ninety liv- 

 ing species are known, most of them living, except Lingula, 

 which is tropical, in the temperate or arctic seas, while nearly 

 2000 fossil species are known. The type attained its maxi- 

 mum in the Silurian age, and in palaeozoic times a few spe- 

 cies, as A trypa reticularis, extended through an entire system 

 of rocks and inhabited the seas of both hemispheres. 



Class V.— BRAOHIOPODA. 



SheUed worms, with a limestone or partly chitinous, iiieguivalve, hinged 

 or unhinged shell, enclosing the worm-like animal ; with two spirally coiled 

 arm,s provided with ciliated cirri or tentacles, between which is llie mouth. 



