CLASS XII. 
CONCHIFERS (CONCHIFERA). 
Wirn LAMARCK we unite all the bivalve molluscs in a single 
class, which also contains the Brachiopoda of Cuvier. ‘They are 
acephalous molluscs, of which the mantle is always more or less, 
and often entirely, cloven into two laminz, and which are covered 
by a bivalve shell. Their respiratory apparatus is external, and 
situated either between the mantle and the body in form of plates, 
or in the substance of the mantle itself. 
The intestinal canal, very various in length, is closely sur- 
rounded by the other viscera. The cesophagus is short, or there 
exists no oesophagus obviously distinct. Ordinarily a stomach is 
present, yet in Ligula the intestinal canal is almost of the same 
width throughout; and in Orbicula also a stomachal expansion is 
not apparent. Salivary glands are not present in the Lamelli- 
branchiata ; in the Brachiopoda it is doubtful whether one of the 
glandular masses, that surround the intestinal canal, is to be 
regarded as a salivary gland*. Largely developed on the other 
hand is the liver, which, as in the rest of the invertebrate animals, 
receives arterial blood alone, and has no gall-bladder. Numerous 
lobes, consisting either of blind sacs or of branching ccecal tubes, 
1 Most of the general works on this class treat also of the rest of the molluscs, and 
have been partly cited above. Here belongs especially the great work of Pott. Com- 
pare besides, the article Conchifera of DESHAYES in Topp’s Cyclopedia of Anatomy and 
Physiology, 1. 1836, pp. 694—716, and R. GarnER, On the Anatomy of the lamelli- 
branchiate Conchifera, Trans. of the Zool. Soc. 11. 2, pp. 87—101, Pl. 18—20. 
2 In Ligula Anatina Cuvier observed a difference of colour in these glandular 
masses, which led him to consider the round white gland, situated in the middle, to be 
salivary, the lateral, divided into many lobes, and yellow brown, to be a liver. OWEN 
could not perceive such difference of colour in Lingula Audebardii, and supposes that, 
in the specimens examined by Cuvier, it was to be ascribed to some accidental cause, 
as bleaching by the spirit in which the animals were kept (Trans. Zool. Soc. 1. p. 157). 
I must, however, observe that the specimen examined by me gave the same results as 
Cuvier has noticed, although I do not regard difference in colour as a certain proof of 
difference in function. In the other genera of Brachiopoda, which I have not examined, 
Terebratula and Orbicula, OWEN found no glands except the liver. 
