THE CARBONIFEROUS PERIOD. 



189 



the shell was permanently attached to some extraneous object, 

 such as the stem of a Crinoid. The two species here figured 

 are interesting for their extraordinarily extensive geographical 

 range Producta semireticulata (fig. 127, a) being found in the 

 Carboniferous rocks of Britain, the continent of Europe, 

 Central Asia, China, India, Australia, Spitzbergen, and North 

 and South America; whilst P. longispina (fig. 127, b) has a 

 distribution little if at all less wide. 



Fig. 121 Carboniferous Brachiopoda a, Producta semireticulata, showing: the 

 slightly concave dorsal valve ; a' Side view of the same, showing the convex ventral valve ; 

 b, Producta longispina, c, Orthia re*upinata; d, Terebralula hastata; e, Athyria aubtU- 

 ita; f, Chonetes Hardrensis , g, Rhynchonella pleurodon ; h, Spirifera trigonalis. Most 

 of these forms are widely distributed in the Carboniferous Limestone of Britain, Europe, 

 America, &c. All the figures are of the natural size. (After Davidson, De Eoninck, and 

 Meek.) 



The higher Mollusca are abundantly represented in the 

 Carboniferous rocks by Bivalves (Lamellibranchs), Univalves 

 (Gasteropoda), Winged-snails (Pteropoda), and Cephalopods. 

 Amongst the Bivalves we may note the great abundance of 



