64 MUSCLES, ARMS AND PINS IN THE CEPHALOPODA. 



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 are fleshy, marked externally by a thin margin which 

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

 surface. The functions of these cupules 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 the^' have the ring 

 itself powerfully armed with recurved points, and greater facilities 

 of attachment on account of having the cupules pedunculated 

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

 of repose these formidable rings are covered by their fleshy 

 borders ; the latter are 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. Enoploteuthis, ana 

 the fossil Beiemnites 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 

 halves of the ring applied closely together. These iiooks are 

 retractile or extensible at the will of the animal, and when 

 retracted are totally enveloped with flesh — recalling the velvet 

 cushion of the paw of a cat. 



The tentacular arms or tentacles of the decapods, always 

 arising from subocular sacks in the circle of sessile arms and 

 between the third and fourth pairs of the latter, are entirely 

 retractile in Sepia, in Sepiola and in Rossia, and only partially 

 so in other genera. Very long (in Chiroteuthis six times the 

 length of the body), the}^ consist of a rounded or compressed 

 stalk, generally without cupules, and an expanded and thickened 

 extremity or cluh, armed with cupules upon its internal face. 

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

 lines upon the club in Loligo and Ommastrephes, six in Histio- 

 teuthisand six or ten in Sepia, Sepiolaand Rossia. Onychoteuthis, 

 Enoploteuthis, Celaeno and Beiemnites have hooks, in two rows; 

 and in the two former there is additionall}'^ a group of small 

 cupules and tubercles at the base which may be used to form by 

 the apposition of these parts in the two tentacles a sort of 

 fleshy articulation and support for the action of the armed 

 clubs. Chiroteuthis has an additional oval fleshy cupule at the 

 extremity of the club. 



The weh which connects the arms in many of the cephalopods 

 may be likened to an umbrella of which the arms themselves 

 may represent the ribs. It is but little developed in some genera, 

 but attains an enormous development in Cirroteuthis (xxiii, 1), 

 where it unites all the arms to nearly their tips ; and in species 



