348 TEREBRATULID^. 



beyond the shell twice its longitudinal diameter. The 

 mechanism by which the arms are extended is single and 

 beautifiil : the stems are hollow from one end to the other, 

 and are filled with fluid, which, being acted upon by the 

 spirally disposed muscles composing the parietes of the 

 canal, is forcibly injected towards the extremity of the 

 arm, which is thus unfolded and protruded outwards. 

 The alimentary canal commences by a small puckered 

 transverse mouth, which is situated, as before mentioned, 

 immediately behind the folded extremities of the arms, 

 and oj)ens opposite the middle line of the perforated valve. 

 The oesophagus, after having passed through the membrane 

 inclosing the viscera, makes a slight turn on itself and 

 advances straight towards the opposite valve ; it then 

 suddenly expands into a large oval stomach, from the 

 sides of which the canals branching out into the hepatic 

 follicles are continued. The intestine returns in a direc- 

 tion towards the perforated valve, inclines to the right 

 side, and makes a slight bend forward before perforating 

 the circumscribing membrane, in order to terminate be- 

 tween the mantle lobes on that side. The whole ali- 

 mentary canal thus forms a loop, whose convexity is turned 

 towards the imperforate or upper valve." * 



The interesting paper of Mr. King, in the eighteenth 

 volume of the Annals of Natural History, has dispelled 

 the doubts which had long been entertained respecting 

 the indigenousness of this species. In it is recorded the 

 fact of a psittacea having been brought up from the depth 

 of thirty fathoms at a distance of twenty-five miles from 

 the northern coast of Northumberland, dead, but hanging 

 on the beard of our common large Modiola. Mr. Maclaurin 



* Owen in Zool. Transactions, vol. i. p. 152. 



