98 MOLLUSCA. 
conical form, the older ones having been effaced in succes- 
sion. The genus Tulaxodes of Guettard is not, perhaps, 
entitled to be considered as distinct. 
The AmpLexvs of Sowerby belongs to this division. It 
is nearly cylindrical, divided into chambers by numerous 
transverse septa, which embrace each other with their re- 
flected margins. It contains one species from the limestone 
rocks of Ireland, but we may add that it has been supposed 
to belong to the zoophytes rather than the mollusca. 
3. Multilocular testacea of a globular form. The first 
genus of this section is the Mrz1oxa. The shell is com- 
posed of three or four oval cells, turning round an axis pa- 
rallel to their longest diameter. Many recent species of 
this genus are common on our shores; they were included 
by Montagu in his genus vermiculum. 
In the Renutrya the cells are narrow, linear, unilateral, 
curved into a part of a circle, and all situate on the same 
plane. The smallest cell forms a little arch round a mar- 
ginal axis, and the others are placed contiguous to this on 
the same side. The species are all fossil. 
The Grrocona was for many years viewed as a shell of 
a spheroidal form, composed of linear, curved, grooved, 
pieces, terminating in two poles, the external surface obliquely 
spiral, the spires terminating at each pole, and as found only 
in a fossil state. But more recent observations have con- 
nected it with the seed vessel of the genus chara. 
The shells of the genus NUMMULITEs are remarkable for 
their lenticular form. The external surface is smooth, and 
the cells concealed, but internally the transverse shells are 
disposed in a spiral discoid form. The cells are imperfor- 
ate; they are the camerine of Bruguiére, the helecites of 
Guettard, and the discolithes of Fortis. This last author 
