166 



MAinJAL OF THE MOLLFSCA. 



suckers in two rows; the third left arm nectocotylised at the 

 apex. 



Diatributiony 2 species. Mediterranean. 



BoLiT^NA. Strp. 1858. 



Similar to Eledone, but more gelatinous, and with small 

 suckers. 1 species living. 



Section 13. — Decapoda. 



Ai^ns 8. Tentacles 2, elongated, cylindrical, with expanded 

 ends. SucJcers ^pedunculated, armed with a horny ring. Mouth 

 surrounded by a buccal membrane, sometimes lobed and fur- 

 nished with suckers. Eyes movable in their orbits. Body 

 oblong or elongated, always provided with a pair of fins. Funnel 

 usually furnished with an internal valve. Oviduct single. Nida- 

 mental gland largely developed. Shell internal ; lodged loosely 

 in the middle of the dorsal aspect of the mantle. 



The arms of the decapods are comparatively shorter than 

 those of the octopods ; the dorsal pair is usually shortest, the 

 ventral longest. The tentacles originate within the circle of 

 the arms, between the third and fourth paii-s ; they are usually 

 much longer -than the arms, and in cheiroteuthis are six times 

 as long as the animal itself. They are comj)letely retractile 

 into large subocular pouches in sepia, sepiola, and rossia ; partly 

 retractile in loligo and sc2noteuthis ; iion-vetiactile in cheiroteuthis. 

 They serve to seize prey which may be beyond the reach of the 

 ordinary arms, or to moor the animal in safety during the 

 agitation of a stormy sea. 



The lingual dentition of the cuttle-fishes somewhat resembles 

 that of the pterovoda. The central teeth are simple in sepia and 



I 



Fig. 39. Lingual teeth of Sepia officinalis (Cocken). 



sepiola, tricuspid in loligo, and denticulated in eledone. The 

 lateral teeth or uncini are three on each side, and mostly simj)le 

 and claw-like. There were fifty rows of teeth in one specimen 

 of sepia, the ribbon increasing in breadth from before to behind. 



