44 M. Valenciennes on the Organization of Lucina and Corbis. 
only mentioned Loripes in order to verify the observations of the 
Neapolitan anatomist respecting the foot of this mollusk, it may 
be conceived why he has not pointed out the absence of one pair 
of branchie. I must however add, that the Lucina lactea, ex- 
amined by these expert zoologists, is a very minute mollusk of 
one to two centimetres in diameter, while I haye been. able to 
examine Lucine from five to, six centimetres in diameter; the 
observation was therefore easy to make ; and when once I had as- 
certained the possibility of the existence of one single branchial 
lamina in Lucina jamaicensis and L. tigerina, 1 could readily de+ 
tect the same organization in the smallest mdividuals of Lucma 
lactea from the Mediterranean. 
The conformation of the foot of these mollusks, which had at- 
tracted the attention of Poli, is very remarkable ; but this anato- 
mist has not given a very complete description of it, which it 
nevertheless deserves. This foot is a fleshy cylinder folded back 
on itself so as to be hidden between, the plates of the mantle of 
the mollusk, for it is frequently twice as long as the diameter of 
the animal. When not contracted it is much longer. It is re- 
markable that it is hollow throughout its entire length, and that 
this tube opens directly and widely into the spaces of the visceral 
cavity. I have verified this fact by followmg the canal in its en- 
tire length either by cutting it open or by injection, when the 
spaces of the visceral mass became filled, and I also thought I 
could perceive traces of injected vessels... This result: wall not 
appear surprising if we call to mind the observations: which 
M. Milne Edwards and I have communicated to the Academy on 
the circulation in Mollusca, and on the large communications ex- 
isting between the visceral cavity and the sanguiniferous vessels 
of the Acephala. But there is a new fact here deserving of 
especial attention, from its importance for the physiology of Mol- 
lusca; itis, that the imner cayities contammg the blood are 
placed by means of the canal of the foot in Lucia im free com- 
munication with the. surrounding element. The heart and the 
other viscera which I was able to observe of these animals, pre- 
served in spirit, did not appear to offer anything remarkable. 
[It is to be regretted that:M. Valenciennes has. not accompanied 
his notice of the smgle gill dmeach: side of thesLucina with some 
account of its structures: from -the »statement that’ it isdange, thick,! 
and formed of pectinated and anastombsingtamelle, it may agree-essen=) 
tially with the apparently single gill-ini the genera Pholadomy« and 
Anatina, described by Prof. Owen in his.‘ Lectures’.on: the _Inver-. 
tebrata,’ 1843, p. 283, where the exception to: the -ordmary strac- 
ture and number of the gills m the Lamellibranchiate Acephala is 
distinctly pointed out as follows :— 
«« ‘The two branchial lamellz of one side are usually connected with 
those of the opposite side by their posterior extremities only; but 
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