2* MUSCLES, ARMS AND FINS. 



IMiiloncxis (Tremoctopus) they arc cylindrical and extensible. 

 Tin- sessile suckers :irc powerful means of prehension; they act 

 like cupping-glasses by the withdrawal of a. central plug. 



The pedunculated cnpulos of the decapods occupy alternately, 

 two lines in all the genera except Sepia, in which they are in 

 four lines. Always very oblique, raised on a narrow excentric 

 stalk, they arc Meshy, marked externally by a thin margin which 

 confines a corneous ring, in the middle of which is an elevated 

 surface. The functions of these cnpnles compared to those of 

 the octopods appear to differ in this respect, that they cannot 

 hold by suction, being prevented by the thin border and corneous 

 ring, but in lieu of this means of prehension they have the ring 

 itself powerfully armed with rmn-rrtJ points, and greater facili- 

 ties of attachment on account of having the cnpules pedunculated 

 and movable, instead of sessile MS in the octopods. In a state 

 of repose these formidable rings are covered by their fleshy 

 borders, which arc only contracted when their weapons are to be 

 used. 



Whilst the corneous circle or ring exists in all decapods, it is 

 modified nevertheless in the different genera, as will be shown in 

 the systematic portion of this work. Enoplotenthis, and the 

 fossil Belemnites offer a curious modification of structure of the 

 corneous ring, which has disappeared apparently, and is replaced 

 by powerful recurved hooks, which are really the two sides of 

 the circle applied closely together. These hooks are retractile 

 or extensible at the will of the animal, and when ret ractcd arc 

 totally enveloped with llesh resembling the velvet cushion of 

 the paw of a cat. 



The tentacular arms or tentacles of the decapods, always 

 :iri>ing from sub-ocular sucks in the circle of sessile arms and 

 between the third and fourth pairs of the hitter, are entirelv 

 retractile in Sepia, in Sepiola and in Kossia. but only partially 

 so in other gencr:i. Very long (in ( 'hiroteiit his six times the 

 length of the body), they consist of a rounded or compressed 

 ^talk. generally without eiipules. and an expanded and thickened 

 extremity or clnl>. armed with cupules upon its internal lace. 

 These cupules or hooks are very unequal in size and occupy four 

 lines upon the club in Loligo and ( hnmast replies, six in Ilistio- 

 teuthis and six or ten in Sepia. Sepiola and Rossia. Onycho- 



