12 LECTURES ON MOLLUSCA. 



ping the whole at once. They can crawl at the rate of seven feet a 

 minute ; and when wishing to go quicker, they blow themselves out 

 like a bladder, and roll over and over with great speed. They 

 were called polypes by the Greeks; and some species bear a strong 

 general resemblance to what are now called polypes, the jelly-fish, and 

 their allies. The cuttles may be said to represent the radiates among 

 the mollusks, but in their organization the} r are as different as birds 

 and butterflies. The genera are Octopus^ Cistopus, Pinnoctopus, Ele- 

 done, and Cirroteuthis. They differ in the arrangement of the suckers, 

 and in the presence or absence of aquiferous pores in the skin and 

 fins on the body. The Eledone moschata emits a strong smell of 

 musk. The Cirroteuthis mulleri has its slender arms ciliated, with a 

 web extending to their extremity. It inhabits the shores of Green- 

 land. The 



Family PHTLONEXID.E 



differ from the typical octopods in being gregarious, living in the open 

 sea. They hide themselves by day ; but towards evening come up in 

 great shoals, to prey upon swimming mollusks and zoophytes. The 

 genera are Philonexis and Tremoctopus. 



GROUP II. DECAPODA. (Ten-footed Cuttles.) 



These differ from the Octopods in having an additional pair of arms, 

 much longer than the others, called tentacles. They are generally 

 club-shaped at the end, and armed with a horny ring round the 

 suckers, or sometimes with claws. They are within the circle of the 

 eight arms, between the third and fourth pairs ; and are (for the most 

 part) capable of being drawn in to pouches behind the eyes. The body 

 is long, always finned, and strengthened by an internal appendage ; 

 which is a horny pen in the squids, a " bone" in the true cuttles; a 

 spiral, chambered shell in Spirula ; a complex organ with a cham- 

 bered shell inside in the Belemnite tribe. The eyes are movable 

 in their orbits ; the breathing funnel is generally provided with a 

 valve ; and the mantle is supported by internal fleshy bands. 



Family CRANCHIAM. 



The Cranchia is a pot-bellied little creature, with very small head 

 and eyes. These are covered by the skin; the mantle is supported by 

 two internal fleshy bands ; and the breathing-pipe has a valve. 



Family LOLIGOPSID.E. (Calamaries.) 



In Loligopsis, which is a very long animal with a small head, the 

 eyes are large and beautiful, and the breathing-pipe is without valve. 



Family CHIROTEUTHID^E. (Hand-Calimaries.) 



The body of the Hand-calamary, (Chiroteuthis,) seems only like a 

 fulcrum, from which to move its powerful head organs. Though only 

 two inches long, the arms are eight inches, and the tentacles extend 



