204 J. Hail on ithe Genus Archimedes or Fenestella. 
Tn all the essential characters, the foliate expansions of Archi- 
medes, correspond to Fenestella, according to the extended descrip: 
tion of this genus given by Mr. Lonsdale, and in detached frag- 
ments it cannot generally be distinguished from other forms of 
the same genus, Some of the species have more than a double 
row of cells on the branches, and correspond to the genus Poly- 
ra of McCoy, but nevertheless this character is found in true 
enestellz as above cited. 
The mode of growth therefore, constitutes the only reliable 
character for separating Archimedes from Fenestella, and should 
this be hereafter considered of sufficient importance, I propose to 
retain the original name of Lesueur, “ Archimedes,” for fossils 
having this character. 
Dr. D. D. Owen has several times alluded to “‘ Archimedes” in 
his various reports; and in a paper published in the American 
Journal of Science and Arts, vol. xliii, p. 19, he gives a figure of 
one of the species as the “ Archimedes of Lesueur,” but suggests 
that it may be only a new species of Retepora. This figure of 
Dr. Owen is of a large species; but being merely the spiral axis 
it furnishes no character for specific identification. It retains the 
thickened base of the foliate expansion, and where this is broken 
rough ro the irregularly cellular structure common to the 
axis of all the species 
This structural character or the remains of the fenestrules on 
the edge of the spire, as seen in the figure, have been mistaken 
by M. D’Orbigny for the animal cells, and upon this character he 
It is quite unnecessary to say that the “Archimedes” of the 
earboniférous 1i © chibi 
i For descriptions of several ies of this genus see proceed- 
mgs > rng mh Aessestiation: for the Advancement of Sci 
