110 



CHAPTER XVIII. 



TEKEBRATULA PSITTACEA, OR PARROT's BEAK. — MEGATHYRIS. — CRANIA, 

 OR THE MASK. — Hl'AL^A AND SPIRALIS. 



TEKEBBATTJLIDJE, CRANIAD^ PTEROPODA. 



Our British representatives of the order BracUopocla are 

 not numerous^ either as to species or individuals. They 

 are distinguished from other orders by the spiral fringed 

 arms which spring from the margins of the mouth; they 

 have no power of locomotion^ but are attached by means 

 of a horny cord passing through part of the shell. The 

 British Terehratulidae, are — 



I, Hypothyris psittacea, or Terehratula psittacea, so 

 named from the curious resemblance in the slate- 

 coloured valves to the beak of a parrot^ the apex of 

 one bending in a produced point over the other. The 

 byssal cord passes through an opening under the beak. 



