155 
of separating these plates, for the purpose of increasing or dimi- 
nishing its degree of buoyancy. The fibrous structure of the plates, 
Fig. 18, appears to be rather confirmatory of its possessing this 
power ; since, should these have been muscular fibres, their action 
would have materially affected the size of these cavities. 
N. complanata. This fossil is smooth, round, very broad, and 
flat, with an undulating margin. 
This species is directly known by its extreme thinness, every 
spiral turn and every septum being perceptible even on the surface. 
One of this species is represented Plate X. Fig. 2 7 ; and Plate X. 
Fig. 21, represents its longitudinal section. By an examination ot 
this section with a single lens, I could not discover any more than 
the upper and under plate. 
Possessing a very interesting mass of nummulites, and other marine 
bodies, which was presented by the Abbe Fortis to Mr. Strange, I made 
it the next subject of my examination. Speaking of the fossils observed 
whilst tracing the course of the Duare to its mouth, the Abbe says : 
“ Further on the road, in the jurisdiction of Slime, are to be seen, in 
great quantities, various kinds of flints of different colours, and 
curious marbly compositions of marine bodies, susceptible of a fine 
polish. I have some specimens, that deserve a place in any museum 
whatever. One, in particular, is an aggregate ot marble, composed 
of lenticulares, fragments of other fossil marine bodies, and white an- 
gular pebbles. Among the small petrified lenticulares contained in this 
marble, some have their concamerations distinguishable on the outside. 
In looking, with the naked eye, on the superfices of this marble, one 
discovers a very great variety of sectionsof the lenticulares contained in 
it- and almost every particle, when examined with a glass, affords some- 
thing agreeable.” Travels in Dalmatia, by Abbe Alberto Fortis, p. 294. 
Of the flints mentioned by the Abbe, in the former part of this para- 
graph, I possess one which is of a light yellowish colour, in which the 
