DEVONIAN AND OLD RED PERIOD. 



143 



ised wasp's nest with the comb exposed is hardly less strik- 

 ing, and has earned for it a similar recognition from the 



Fig. 84. — Portion of a mass of Favo- 

 sites Gothlandica, of the natural size. 

 Upper Silurian and Devonian of Europe 

 and America. (Original.) 



Fig. 85. — Fragment o{ Favosites hemi- 

 spherica, of the natural size. Upper Silu- 

 rian and Devonian of America. (After 

 Billings.) 



non-scientific public. In addition to these, there are numer- 

 ous branching or plant-like Tabulate Corals, often of the most 

 graceful form, which are distinctive of the Devonian in all 

 parts of the world. 



The Echinodernis of the Devonian period call for little 

 special notice. Many of the Devonian limestones are "crin- 

 oidal;" and the Crinoids are the most abundant and widely- 

 distributed representatives of their class in the deposits of 

 this period. 



The Cystideans, with doubtful exceptions, have not been 

 recognised in the Devonian ; and their place is taken by the 

 allied group of the " Pentremites," which will be further spoken 

 of as occurring in the Carboniferous rocks. On the other hand, 

 the Star-fishes, Brittle-stars, and Sea-urchins are all continued 

 by types more or less closely allied to those of the preceding 

 Upper Silurian. 



Of the remains of Ringed-worms (Annelides), the most numer- 

 ous and the most interesting are the calcareous envelopes of 

 some small tube-inhabiting species. No one who has visited 

 the seaside can have failed to notice the little spiral tubes of 

 the existing Spirorbis growing attached to shells, or covering 

 the fronds of the commoner Sea-weeds (especially Fucus ser- 

 ratus). These tubes are inhabited by a small Annelide, and 

 structures of a similar character occur not uncommonly from 

 the Upper Silurian upwards. In the Devonian rocks, Spir- 

 orbis is an extremely common fossil, growing in hundreds 

 attached to the outer surface of corals and shells, and appearing 



