158 
change of specific gravity. Thus also, in those which have been last 
described, should they have been of alcyonic structure, the action of 
the muscular fibres would have occasioned such changes of form as 
are here noticed, and as would, by enlarging or lessening their cen- 
tral cavity, necessarily affect their buoyancy. 
These fossils are found in prodigious quantities, in mountainous 
masses, in different parts of Hungary, Transylvania, Switzerland, 
France, and Italy. But perhaps these fossils exist no where in more 
abundance than in Tuscany ; where, according to Targioni Tozzetti, 
they are to be found, particularly in the mountain of Parlascio, 
forming strata three yards in thickness, and mixed with all the 
several minute shells which have been figured by Bianchi, in his work, 
De Conchis minus notis, 8fc. Voyage en Toscane, fyc. Tome n. p. 148. 
To my kind correspondent, Mr. J. Holloway, of Portsmouth, I 
am very much obliged for being enabled to ascertain the existence of 
these fossils in this island. This gentleman furnished me with 
several of N. laevigata , from Stublington Cliff, between Stokes’ Bay 
and Southampton Water. 
Although from the minuteness, as well as the imperfect state of the 
few specimens of which I possess, I may be unable fully to develope 
the structure and determine the nature of the fossil now placed before 
you, Plate X, Fig. 28, it is yet hoped, that sufficient will be shown 
to render it interesting. An examination, with a powerful lens, was 
necessary, to discover most of those peculiarities, in the structure of 
this fossil, which will be noticed in its description. 
LXXXIII. Fasciolites. A subcylindrical, shelly, or bony body, 
about half an inch in length, rather tapering at the ends, and formed 
by the spiral arrangement of the perpendicular, concamerated tubes, 
the tapering end of each of which is obliquely and transversely 
folded on that of the preceding one. 
The appearance which this fossil offers to the naked eye is shown 
