SYNOPSIS OF THE FAMILIES. 
Class—Cephalopoda. 
Mouth surrounded by 8 or 10 fleshy arms. 
Order—Ocroropa.—Arms eight. 
Family—Octopide.—All the arms tapering - - - 
a Argonautide.—The two dorsal arms webbed at the extremity 
Order—Decapopa.—Arms ten. 
Family—Onychoteuthide.—Kyes naked, shell horny — - . - 
55 Loligide.—Eyes covered with skin, shell horny - - 
~ Spirulide.—Shell calcareous, spiral - - - - 
Class—Gasteropoda. 
Head distinct, creeping by means of a foot. 
Order—Pu.Lmonata.—Mantle cavity closed in front. 
Sub-order—STYLOMMATOPHORA. -—Eyes stalked. 
Family—Oleacinide.—Body spiral ; head short ; teeth in curved rows - 
a Helicide.—Body spiral ; head large; teeth in straight rows ; 
mantle not produced - - = - : 
% Stenopide.—Body spiral, mantle produced into lobes ; a cau- 
dal gland - - 2 
5 Limacide.— Body elongate, mantle small ; no ada ba - 
BA Arionide.—Body elongate, mantle small ; ’a caudal gland : 
50 Janellide.—Body elongate, mantle radimentary ; tentacles 
two only - - - - - 
Onchidiide. —Body not spiral, mantle large ; meine - - 
Sub- order--BASOMMATOPHORA. —kKEyes sessile. 
Family—Limneide.—Tentacles flattened or filiform ; fresh water 
$5 Auriculide.—Ventacles sub-cylindrical - - - 
5 Amphibolide.—A horny operculum — - = : 
e Siphonariide.—Shell simple, conical, marine ; uentaules flat- 
tened into a frontal disc - . - = 
Pe Gadiniidie.—Shell simple, conical, marine ; tentacles ex- 
panded, funnel-shaped - - J e 
Order—Brancutata.—Mantle cavity absent, or open in front. 
Sub-order—PRosoBRANCHIATA.—Gills in front of the heart. 
Division—NEUROBRANCHIATA.—Breathing air by a vascular net work 
in the mantle cavity. 
Family—Cyclophorid@.—Kyes at the outer bases of the tentacles - 
os Assiminiide.—Kyes on the tentacles near their tips - - 
Division— CreNOBRANCHIATA.—Gills pectinate, the upper wall of the 
mantle cavity generally prolonged into a siphon; dentition 
never ripidoglossal. 
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