314 



ANNULOSA. 



185) ; and similar forms are found in the Carboniferous. The 

 Spirorbis carbonarius (fig. 186) of the latter formation is an 

 abundant and well-known type, and is remarkable for being 

 not uncommonly found attached to the exterior of fossil 

 land-plants, which leads to the belief that it must have lived 

 plentifully in the salt-marshes of the Carboniferous coasts. 



Fig. 184. a, SpirorUs ompJialodes, natural size and enlarged Devonian, Europe and 

 America ; b, Spirorbis Arkonensis, of the natural size and enlarged ; c, The same, with the 

 tube twisted in the reverse direction Devonian, America. (Original.) 



Fig. 185. a, b, Spirorbis laxus, enlarged Upper Silurian, America ; c, Spirorbis spinuliferus, 

 of the natural size and enlarged Devonian, Canada. (After Hall and the Author.) 



Fig. 186. Spirorbis (Microconchus) carbona.rius, natural size, attached to a fossil plant, 

 and magnified Carboniferous. (After Dawson.) 



Other species have been described from the Permian, arid 

 the genus continues to be well represented in both Mesozoic 

 and Tertiary deposits ; while living forms, apparently little 

 different from the fossil ones, abound in recent seas. 



The genus Serpula (fig. 187) possesses a long shelly tube, 

 usually more or less tortuous, sometimes solitary, sometimes 

 aggregated, and fixed to some foreign body by part of its 



