. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . us other genera of shell-bearing cephalopods,indicate that this group has seen its best days. The dibranchiategenera, however, appear to have reached their maximum at thepresent day. SUBCLASS DIBRANCHIATA The second subclass, the Dibranchiata, is characterized by twobranchiae and two auricles. The main part of the foot is dividedinto eight or ten long arms provided with numer-suckers arranged in from one to four rowsu the ventral side of the arms. They havealso an ink-sac. The
. The sea-beach at ebb-tide : a guide to the study of the seaweeds and the lower animal life found between tidemarks . us other genera of shell-bearing cephalopods,indicate that this group has seen its best days. The dibranchiategenera, however, appear to have reached their maximum at thepresent day. SUBCLASS DIBRANCHIATA The second subclass, the Dibranchiata, is characterized by twobranchiae and two auricles. The main part of the foot is dividedinto eight or ten long arms provided with numer-suckers arranged in from one to four rowsu the ventral side of the arms. They havealso an ink-sac. The Dibranchiata aredivided into two orders: the Octopoda,which have eight arms, and comprisethe Octopus and Argonauta; and theDecapoda, which have ten arms,and comprise Spinda, Omma-strephes, Sepia, and these animals two ofthe ten arms are longerthan the others, andthesetentacular arms havesuckers only on their/9 ^Vvtg^i) broadened, club-like cT^^^-tiLv ends, they are keptretracted withingrooves, one on eachside of the head, ex-cept when needed for Argonauta aryo, female removed from shell. picllollol CEPHALOPODS 41 ill GEMS Art/on ft Ufa A. fitf/o. In this species, the paper-nautilus, the slid), which is pos-sessed only by the female, is not chambered. The animal rests in theshell, but has no or-ganic connectionwith it other than bythe membranous e\-pan-ions at the ex-tremities of the twodorsal arms, whichsecrete it and hold itin place. The pur-pose of the shell ist<» hold and protectthe eggs. <;i:.\rs Lotif/o
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmarinea, bookyear1901
