XI. SYNOPSIS OF THE FAMILIES. 
PAGE 
Class—Lamellibranchiata. 
Shell of two valves, placed laterally. 
Order—Isomya.—T wo equal adductor muscles. 
Section—SinuPauLraTa. —Pallial line with a deep sinus. 
Sub-order— PuHoLapacra.—Gills prolonged into the lower siphon. 
Family-—Pholadide.— Auimal worm like, interior of valves with a long 
curved process - - - - - a ay 
Sub-order—Myacka.—Siphons long, united, gills not extending into 
them. 
Family—Glycimerid@,— Mantle closed, thickened in front, with a small 
anterior orifice ; shell equivalve, gaping - - - 134 
A Corbulid@.—Mantle closed, except a small anterior orifice ; 
shell inequivalve, closed - - - - - 135 
53 Anatinide.—Mantle closed; siphons more or less separate ; 
cartilage in an internal pit - - - - - 135 
= Mactride.—Mantle open beneath ; cartilage in an internal 
triangular pit - - = - - - 138 
Sub-order—TELLINACEA.—NSiphons long, completely separated ; gills 
unequal. 
Family — Tellinid@.—Ligament external ; cartilage none - - 141 
as Paphiide.—Cartilage in an internal pit, shell closed - - 145 
Sub-order— VENERACEA—Siphons moderate, mantle wide open in 
front ; gills equal. 
Family— Veneride@.—Shell closed ; three diverging cardinal teeth in 
each valve - - - - - . - 146 
Petricolide.—Shell gaping ; two unequal teeth in each valve - 153 
9 
Section—INTEGROPALLIATA.—Pallial sinus small or none. 
Sub-order—CyprinacEea.—Gills two on each side ; unequal. 
Family —Cardiide.—Marine ; shell generally radiately ribbed - - 153 
Oyrenide.—Fresh water ; shell covered with an epidermis — - 
Sub-order—Luctnacea.—Gills one on each side. 
Family—Lucinide.—Mantle free ; one gill on each side - - 1 
Ungulinide .—Mantle united below ; two gills on each side - 1 
Lascide.—Mantle folded anteriorly into a tube - - 1 
I 
] 
99 
99 
Solemyide.—Shell invested with a thick epidermis — - 
Astartide —Hinge large and solid - : - = 
99 
99 
Sub-order— UnronackaA.—Fresh water ; gils four ; mantle margin 
free ; shell with a thick epidermis. 
Family— Unionide.—Byssus none ; shell equivalve : 2 - 160 
Sub-order—A RcAcEA.— Mantle margin free ; hinge with many teeth. 
Family—A rcide.—Hinge teeth continuous ; shell not pearly within - 162 
a Nuculide —Hinge teeth interrupted in the middle ; no si- 
phonal tubes - > - - - - 168 
A. Ledide.—Hinge teeth interrupted in the middle ; siphonal 
tubes united - - - - - - 165 
Order—Hereromya.—-Aductor muscles two, unequal. 
Family—Mytilide.— Hinder part of the mantle produced into a siphon ; 
umbones anterior ; shell covered with an epidermis - 166 
be Aviculide.—No siphon ; shell fohated - - - 169 
Order—Monomya-—One adducter only. 
Family— Pectinide.—Foot byssiferous, not expanded; shell eared ; 
closed - - = - - - - 170 
Radulide.—Foot not byssiferous ; shell eared, gaping at the 
sides = - - - a ie Pa 172 
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