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muscular system in these animals appears to be most complex ; the 
Lingule and Orbicule are provided with three pairs of muscles, and 
the Terebratule have four. The large muscles are destined to open 
and close the shell in the absence of a hinge ligament; and the 
small ones assist in sliding one valve over the other for the admis- 
sion of water. 
“Until within the last few years only one species of Lingula was 
known, and previous to the publication of Cuvier’s memoir, before 
alluded to, the shell of this singular animal gave rise to much specu- 
lation amongst naturalists. Linnzus, upon the discovery of an odd 
valve of Lingula exhibiting no trace of any hinge ligament, described 
it as a Patella. Both Rumphius and Favanne took it to be the 
calcareous shield of a Limaz or land-slug. Chemnitz, upon finding 
that the shell of Lingula was really bivalve, placed it with the Pinne; 
and even Dillwyn includes it with the Mytili. Bruguiére was the 
first to distinguish it by its present title in the plates of the ‘ Ency- 
clopédie Méthodique,’ in which he has been followed by Cuvier, La- 
marck, and all succeeding writers. 
“With regard both to the situation that the Brachiopodous Mol- 
lusca should occupy in the natural system, as well as the rank to 
which they are entitled in the classification, authors have been much 
divided. By Dumeril and De Roissy they were associated in a par- 
ticular class with the Lepades, on account of a fancied resemblance 
in their spirally twisted arms to the cirrous tentacula of those ani- 
mals ; they differ however in not being articulated, and their relation 
altogether with the Lepades is one of very remote analogy. Cuvier 
distinguished them as a new and separate class, but still arranged 
them next in order to the Lepades. Lamarck placed them at the end 
of his ‘ Conchiferes monomyaires’ merely as a family of that order. 
Prof. Owen and Deshayes both consider that they are entitled to 
take the rank of an order; the latter author however admits that 
there is far less affinity between the Brachiopoda and the rest of the 
acephalous mollusks, than there is between the acknowledged divi- 
sions of Bimuscular and Unimuscular. In the arrangement of my 
‘Systematic Conchology’ I propose to adopt the still higher rank 
that was assigned to them by Cuvier, namely, that of a class, placing 
them according to Lamarck, at the end of the Acephala, upon the 
presumption that their branchial apparatus presents a modification 
of structure intermediate between that of the proximate classes, the 
Tropiopoda and the Gasteropoda. 
“The Lingule come with great propriety at the commencement of 
the class, because they have the nearest affinity with the Tropiopoda; 
their body is larger in proportion to that of the rest of the Brachio- 
poda, and although the branchiz are incorporated within the sub- 
stance of the mantle, they nevertheless present a certain indication 
of the lamellar structure. Lamarck placed them at the end of his 
family of ‘ Les Brachiopodes,’ because, in having referred the Cranie 
to his fossil family of ‘ Les Rudistes,’ he found it necessary to follow 
up their affinity with the Orbiculg; his arrangement of the genera 
therefore is the reverse of that I have adopted. 
