SYSTEMATIC 
ARRANGEMENT OF CONCHIFERA. 
CLASS XII. 
CONCHIFERA. 
ANIMALS without distinct head, covered on each side with 
a lamina of mantle. Shells two, incumbent on mantle. Heart 
aortic. Respiration branchial, with branchiz mostly lamellose, 
running out near the margins of body on each side, covered by 
mantle; in some the mantle itself discharging the office of 
branchiz. Some hermaphrodite, others with sex distinct: all 
aquatic. 
OrveEr I. Palliobranchiata or Brachiopoda. 
Body depressed, covered with mantle, bilobed, open. Branchiz 
grown to the mantle or not distinct from mantle. Heart double, 
arterial. Two long arms convoluted in form of a spiral, armed 
with cirri or cilia. Mouth simple at the base of arms. Shell 
bivalve, affixed, sessile or petiolate, adhering to mantle by several 
oblique muscles. 
Family I. Brachiopoda. Characters those of the order. 
On this order and family may be compared :— 
Cuvier Mém. sur 2Animal de la Lingula, Ann. du Mus. 1. 1802, 
pp. 69—80, Pl. v. reprinted in his Mémoires sur 0 Hist. et [ Anat. 
des Mollusq. No. 21. 
Broperip Descriptions of some new species of Brachiopoda, Trans. 
Zool. Soc. 1. pp. 141—144. 
