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 Producte, 
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 
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Fig. 127.—Carboniferous Brachiofoda. a, Producta semireticulata, showing the 
slightly concave dorsal valve; a’ Side view of the same, showing the convex ventral 
valve; 64, Producta longispina; c, Orthis resupinata; d, Terebratula hastata; e, 
Athyris subtilita; 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 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—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 
