April, 1899. j Foord. — Carboniferous Brachiopoda and Mollusca. JJ 



Brachiopoda. 



I have associated the Brachiopoda with the Mollusca, not 

 because there is any connection between the two groups, 

 which are widely separated zoologically, but because they are, 

 like the Molluscs, of great importance as fossils, and well re- 

 presented in the Carboniferous fauna. 



To the naturalist the Brachiopoda have an archaic and quaint 

 air about them which, I think, gives them a peculiar interest. 

 They have hitherto foiled all attempts to ascertain their exact 

 position in the animal kingdom, but this mystery as to their 

 origin does not rob them of their attractiveness. They 

 were called " lamp-shells " by the old naturalists of about a 

 hundred years ago, on account of a fancied resemblance in 

 their shells, when lying on the larger valve with the beak 

 upwards, to an antique lamp. 



The Brachiopoda constitute an isolated tribe or phylum of 

 the animal kingdom having no affinities with the Mollusca, 

 which they simulate in their bivalved shell, and with which 

 they were originally united by Cuvier. One or two striking 

 differences may be pointed out between the two groups ; there 

 is nothing comparable in the Mollusca with the tentaculated 

 "buccal groove," forming the characteristic " spiral arms" of 

 the Brachiopoda, whose calcareous supports are sometimes 

 preserved in the fossil state. Moreover, the shell is dorsal 

 and ventral to the animal's axes in the Brachiopoda, left and 

 right in the Lamellibranchiata, the group they most resemble 

 externally. Nor is there any relationship between the 

 Brachiopoda and the Polyzoa (or Bryozoa — " moss-animals," 

 whose remains are found abundantly in the Carboniferous 

 Limestone) from which they differ in having a vascular 

 system, setae (bristle-like organs) embedded in the skin, a 

 bivalved shell, and in being of a solitary habit, instead of 

 forming aggregations or colonies like the Polyzoa. On the 

 other hand, recent researches point to the relationship of the 

 Brachiopoda to the Annelida, but to discuss the ground for 

 this connection would lead us beyond the scope of the present 

 communication. Like many other classes of invertebrate 

 animals, the Brachiopoda existed in the very earliest age of 

 animal life known to the geologist, that is, the Cambrian, and 

 they flourish still, though in much diminished numbers. 



A 



