294 SHELLS AND SHELL-FISH. PART i. 



the valves themselves. Besides this set of muscles, and 

 within them, is another set, which passes laterally from 

 one papilla to another. Other muscles enable the ani- 

 mal to contract or dilate itself. The ovaries, viscera, 

 &c., were in too decayed a state for examination ; but 

 the mantle appears to adhere only to the orifices, each of 

 which has six valves.* Wherever this animal is'placed, 

 its extraordinary analogy to the Cyclobranchia and the 

 other cheloniform types, will still be the same; and our 

 present impression is, that it represents the chitons in 

 this division of the order rather than in that of the Tu- 

 nicata. 



(274.) Having now completed our exposition of the 

 two great typical divisions of the TESTACEA, in which 

 are included the whole of the univalve and bivalve shell- 

 fish f, we must reluctantly close this part of our volume. 

 The whole of the aberrant orders, as the Cephalopoda, the 

 Parenchymata, and the Nudibranchia, together with the 

 radiated and the coralline Mollusks, will therefore re- 

 main open to future investigators of the natural system, 

 and they may possibly form hereafter the subject of 

 another volume supplementary to this. 



* Abridged from ZooL Journal, vol. v. p. 46. 



f Excepting thoge of the Cephalopoda or Nautilus order. 



