CHAPTER V 
THE LAMELLIBRANCHIA 
CLASS IV.—THE LAMELLIBRANCHIA, BuaINnvILLE 
(= ACEPHALA TESTACEA, Cuvier ; CONCHIFERA, Lamarck ; 
PELEcypopA, Goldfuss ; LIPOCEPHALA, Ray Lankester). 
Order 1. Protobranchia. 
Sub-Order 1. Solenomyacea. 
#3 2. Nuculacea. 
Order 2. Filibranchia., 
Sub-Order 1. Arcacea. 
2. Trigoniacea. 
ee 3. Mytilacea. 
4. Pectinacea. 
et 5. Dimyacea. 
Order 3. Eulamellibranchia. 
Sub-Order 1. Ostraeacea, 
Submytilacea. 
Tellinacea. 
Veneracea. 
Cardiacea. 
Chamacea. 
Myacea. 
Adesmacea. 
Anatinacea. 
Order 4. Septibranchia. 
Sub-Order. Poromyacea, 
DID OP 9 Lo 
Definition—The Lamellibranchia are Molluscs with an internal 
and external symmetry. The cephalic region is rudimentary, and 
the mantle, divided into a right and a left lobe, secretes a bivalve 
shell which covers and encloses the whole body. The cephalic region 
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