1900.] A BARE CUTTLEFISH. 



995 



three pairs, near the base of which they are each about 1 inch 

 broad. 



The muscular folds that connect the bases of the arms externally 

 are as follows : — A fold or web connects the bases of the ventral 

 and ventro-lateral arms, forming the outer wall of a hollow, about 

 2 inches in depth, within which the tentacle arises. This web 

 is attached to the outer or aboral surface of the ventro-lateral arm, 

 which it crosses to form a similar narrow web or festoon extending 

 to the postero-lateral arm. In the case of the ventral arm it is 

 continued all the way up the dorsal margin in the form of a deep 

 thin frill or keel lying not far distant from the smaller web 

 adjacent to the suckers : a little way from the base this keel is 

 about If inches broad. Corresponding to it on the^ opposite or 

 ventral margin is a very much narrower keel, which appears, 

 however, only to commence about 4 inches from the base of 

 the arm ; above this point it quickly grows to about half an inch 

 in breadth, and extends, slowly narrowing, to about halfway up the 

 arm. In the case of the dorsal arm, there is a very rudimentary 

 keel on the outer side, which does not pass over to join the dorso- 

 lateral arm. The dorso-lateral arm has a well-developed keel on 

 the ventral side, which joins the ventro-lateral arm. 



There is yet another series of folds or membranes connected 

 with the bases of the arms, external to the circumoral membrane. 



Firstly, a muscular fold runs from the internal aspect of the 

 ventral arm to its fellow on the one hand and to the oral aspect of the 

 ventro-lateral arm on the other, marking off here the oral boundary 

 of a cavity or pouch, which is separated by another similar fold 

 from the cavity out of which the tentacle arises, but out of which 

 comes to the tentacle a special fold of membrane within which 

 appears to lie the tentacular nerve. In Ommastreplies the inner 

 of the above muscular folds appears to be absent, the homologous 

 pouch being bounded outwardly by the wall of the tentacular sac 

 and inwardly by the buccal membrane. Another muscular fold, 

 belonging apparently to the same series, unites the inner aspects 

 of the 2nd and 3rd, and 3rd and 4th arms respectively, so that 

 between the bases of each of these pairs of arms is a slight pouched 

 cavity somewhat similar to that from which, between the 1st and 

 2nd, the tentacle grows. 



The suckers are in two rows, and commence on the dorsal 

 arm about 2 inches, and in the others about 3 inches from the 

 base. In the two rows the suckers are obliquely opposite one 

 another, and their bases near the base of the ventral arm are about 

 one inch apart in the case of two opposite suckers, and a little more 

 in the case of two contiguous ones on the same side. There are 

 on the ventral arm about fifty distinct pairs, beyond which for about 

 2 inches at the distal end of the arm the paired arrangement is not 

 clearly maintained. The suckers on the major portion of the ventral 

 arm are about -f^ inch diam., those on the other arms being percep- 

 tibly larger, about | inch diam., towards the middle of each arm. 

 The ventro-lateral arm has about 29 pairs of suckers, and then for 



Pboc. Zool. Soc— 1900, No. LXV. 65 



