FOSSIL LAMP-SHELLS 



225 



The common name of " lamp-shells," given both 

 to fossil and recent species of Brachiopoda, is due to 

 the resemblance of the two valves, ventral and dorsal 

 (minus the handle), to an old Etruscan or Roman 



Fig. ig-^.— A iry/a re- 

 ticularis, showing 

 internal spiral coil 



(Silurian formation). 



Fig. 194.— 0/'^/«5, show- 

 ing internal loop. 



Fig. 1 9 5 . — Pen tnvienis Knigh tit 

 (Upper Silurian limestone). 



lamp. The ventral valve is the larger, and usually 

 has a perforation in the upturned beak, exactly like 

 that through which the wick passed in the ancient 



Fig. 196. — Pentavierns, showing 

 internal plates. 



Fig. \^T.—Orthis eleganinla 

 (Silurian). 



lamps. Older naturalists were, of course, more 

 affected by external appearances than by internal 

 structure— even supposing they took any notice of the 



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