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when the mandible is depressed. The articulation, in fact, between 

 the mandible and cup, bears a close resemblance to the joints of the 

 Articulata in general. When partially closed, the point of the man- 

 dible comes close to the beak of the cup, but when completely de- 

 pressed it lies within the latter, like the lower mandible of a parrot 

 within the upper. The two beaks then would appear to constitute an 

 admirable instrument of prehension. In the interior of the cup are 

 contained two pairs of muscles, and a peculiar body of unknown 

 nature. Of the muscles, one pair, and that much the larger, is for the 

 purpose of depressing, and the other pair, for the purpose of elevat- 

 ing the mandible. The former, or occlusor muscles, form on each 

 side of the cup a fan-shaped expansion ; the broad part of the fan 

 extending across the bottom of the cup, from before to behind. The 

 muscles are composed of strong fibres, which are marked with 

 distinct and regular transverse striae, in all respects like those which 

 characterize the voluntary muscles in the higher classes of animals. 

 These fibres appear to form small bundles or fasciculi, each of which 

 terminates abruptly in a narrow tendon, the union of all which ten- 

 dons goes to constitute the common tendon of each muscle, and the 

 conjoined tendons of the two ultimately constitute the tendon which 

 is inserted into the mandible at the point above indicated : the func- 

 tion of this pair of muscles is evidently to close the mandible, slowly 

 and with force. The other pair, or the elevator muscles, are placed 

 in the back of the cup, from the posterior wall of which they arise and 

 are inserted into the base of the mandible. Their position and size 

 would indicate that their function is to open the cup by elevating the 

 mandible, and that this motion is effected with rapidity, and without 

 much power. This difference in the respective actions of the two 

 pairs of muscles is shown very clearly in the motions of the mandible 

 during life : it opens suddenly with a sort of snap, and is closed 

 slowly. The bottom of the cup is entire. 



The polype-cells are several times larger than the cups, and their 

 walls are much thinner, in fact, sufficiently transparent to allow of 

 the contents of the cell being pretty well seen without any prepara- 

 tion, even during the life of the animal. In shape they are inversely 

 conical, and the outer and upper angle is usually produced into a 

 prominent, sharp point. From the internal and upper angle arises the 

 tubular prolongation going to form the next cell or cup, as the case 

 may be, in succession. They are entirely closed at the top, contrary 

 to what is stated in all previous notices, and, as has been shown, there 



