THE CARBONIFEROUS PERIOD. 



I8 5 



grown shell of an opening in or between the valves for the 

 emission of a muscular stalk for the attachment of the shell to 

 foreign objects. It is probable, therefore, that the Products, 

 unlike the ordinary Lamp-shells, lived an independent exist- 

 ence, their long spines apparently serving to anchor them 

 firmly in the mud or ooze of the sea-bottom ; but Mr Robert 

 Etheridge, jun., has recently shown that in one species the 



Fig. 127. Carboniferous Brachiopoda. a, Producta semireticulata, showing the 

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

 valve; b, Prodncta longispina; c, Orthis resupinat* ; d, Terebratula hastata ', e, 

 A thyris subtilita ', f, Chonetes Hardrensis ', g, Rhynchonella pleurodon ; A, 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 David- 

 son, De Koninck, and Meek.) 



spines were actually employed as organs of adhesion, whereby 

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

 Carboniferous rocks of Britain, the continent of Europe, 

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



