Monthly Microscopical I 
Journal, May 1, 1869. J 
Parkeria and Loftusia. 
303 
of many Alveolinm and Fusuli7im ; being a long oval, frequently 
tapering almost to a point at either end, though sometimes 
obtusely rounded at its extremities. Of two large and perfect 
examples in the collection of the late Mr. Loftus, one measures 
3J inches by 1 inch, the other 2J inches by IJ inch. A trans- 
verse section at once indicates that the plan of growth is a 
spiral, formed by the winding of a continuous lamina around an 
elongated axis ; the general disposition of the chambered structure 
being very similar to that which would be produced if one of the 
simple Botalians were thickened and drawn out at the umbilici. 
The space enclosed by the jprimary lamina is divided into cham- 
bers by longitudinal septa, which may be regarded as ingrowths 
from it, extending, not perpendicularly (as in AlveoUna), but 
very obliquely. The chambers, separated by these principal or 
secondary septa, are long and very narrow, and extend from one end 
of the body to the other. Their cavities are further divided into 
chamberlets or cancelli by tertiary ingrowths, which are generally 
at right angles to the septa, or nearly so, but are otherwise irregular 
in their arrangement. No large primordial chamber, such as is 
common among Foraminifera, has been yet discovered in Loftusia ; 
but its absence cannot be certainly afiirmed. In fully-grown speci- 
mens the turns of the spire, which succeed each other with tolerable 
regularity at intervals of from JqUi to ^yh of an inch, are usually 
from twelve to twenty in number ; but as many as twenty-five have 
been counted in one instance, and a yet larger number might not 
improbably be met with. The spiral lamina and its prolongations, 
forming the accessory skeleton, are all constructed of almost impal- 
pable grains of sand, which is proved by analysis to have consisted 
of Carbonate of lime, united by a cement of the same material. 
The Author then describes in detail the several components of 
the fabric of Loftusia, and compares them with the corresponding 
parts of Parkeria. The continuity of increase of the spiral lamina 
always leaves an open fissure between its last-formed margin and 
the surface of the previous whorl ; and through this aperture the 
whole system of chambers included within its successive laminss 
communicates with the exterior through the passages between their 
cavities, which are left in the building up of the septa. As already 
explained, the labyrinthic structure takes its origin from the inner 
surface of the impervious spiral lamina, the septa being directed 
towards the central axis. These ingrowths have in many instances 
the form of tubular columns, which traverse the chambers in a 
radial direction (i. e. perpendicular to the spiral lamina), terminating 
either on the septum of the previous chamber, or on the exterior 
wall of the preceding whorl of chambers. But these tubes do not 
seem to be homologous with the radial tubes " of Parkeria, whose 
relations differ in important particulars. The range of variation 
