TWO GIGANTIC TYPES OE AEENACEOUS FOE AMINIFEE A . 
753 
by the first turn of the spiral lamina, and about half the circuit of the 
layer immediately surrounding it. 
Sections of several other Foraminifera included in the matrix are seen. 
PLATE LXXVIII. 
General view of the structure of Loftusia, showing the appearances of sections cut on 
different planes, and their relation to each other. — Magnified about 4 diameters. 
PLATE LXXIX. 
Fig. 1. Longitudinal section of Loftusia, very near the periphery, viewed as an opake 
object. — Magnified 45 diameters. 
s l. Imperforate primary skeleton or spiral lamina. 
a. Series of parallel, columnar, secondary shell structure, immediately 
lining the primary lamina. 
c. The same cut transversely. 
It must be borne in mind that this is not a central section, but a tangential one cut 
so near the periphery that the direction of the section differs in its relation to each 
successive layer, so as to illustrate fully the arrangement of the accessory skeleton. The 
centre, representing the innermost of the four layers of which portions are drawn, shows 
at c the appearance presented by the parallel columnar shelly processes (a, a) when cut 
across. The portion of the figure to the right exhibits a mass of the accessory skeleton 
formed from overlapping septa, and shows the sort of intercommunication between them. 
Owing to the direction of the section, or possibly to accidental causes, the spiral lamina 
(s l), the continuity of which is usually a prominent character, appears lost at the end of 
the layers to the right, though well seen in the other portions of the specimen. 
Fig. 2. A portion of a transverse section, s l represents the spiral lamina, and at b its 
distinctness from the accessory structures may be noticed. This condition 
may be found at points in almost every specimen. The nature of the septa, 
as prolongations of the series of columnar processes (a, a, a ) lining the pri- 
mary lamina, may be easily traced. The subdivision into chamberlets, a 
large chamberlet ( c c, cc,c c ) occupying the centre of each chamber (see § 39), 
is also apparent. — Magnified 45 diameters. 
Fig. 3. Longitudinal section of a portion of a layer near the end of the central axis. 
At this point, where the layer is widest and the chambers thin out and over- 
lap, the intercommunication of the septa is often so regular and complete 
that it resembles very strongly the portions of ParJceria in which the system 
of radial tubes is most developed. 
mdccclxix. 5 H 
