THE CARBONIFEROUS PERIOD. 



185 



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 Froductce, 

 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, Producta longispina; c, Orthis resupinata ; d, Terebratula hastata ; e, 

 A tkyris subtilita ; /, Chonetes Hardrensis ; g, Rhyticlt07tella pletirodon ; h, Spirifera 

 trig07talis. 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- 

 pon, 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 — 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 



