58 
Parker^ 07i Miliola. 
varied of any group of the Foraminifera. They may be 
polished, scabrous, or sanded; marked by crests, ribs, or 
riblets ; by pits of varying sizes, and honey-comb sculpturing. 
The ribs may be straight or sinuous, parallel with the cham- 
ber or oblique, continued or broken. The pitted sculpture 
usually aflPects the polished shells. The arenaceous indivi- 
duals vary very much according to the size and character of 
the sandy material of the sea-bed of their several localities. 
Ornamentation in Miliola, as in other Foraminifera, cannot 
be depended on as specific character. 
Size is no criterion. The same variety retains its fea- 
tures whether it be -ri^th or y^oth of an inch in length. 
(These are about the extreme limits of size for Miliolse.) 
The overlapping of the chambers occurs in such varying 
extent, and by such gentle gradations, that no line can be 
drawn marking any species as being characterised in this 
respect. The symmetrical arrangement of the chambers is 
persistent in Spiroloculina and Biloculina, but lost in the 
varieties included under the names Quinqueloculina and 
Triloculina. 
The construction of Miliola is essentially the same through- 
out the above-named varieties — Spiroloculina, Biloculina, 
Quinqueloculina, and Triloculina. The differences arising 
from the asymmetrical growth — from variations of the cylin- 
drical, flattened, or squared form of area of chamber — of the 
relative width or contraction, or of its length or shortness — 
must not be regarded as of specific value. 
If the forms kept themselves as distinct as those repre- 
sented in the diagrams, a naturalist might be excused for 
regarding them as separate types ; but between any two of 
these there may be readily found innumerable gradations, in 
large and in small specimens, in the smooth and the orna- 
mented, in the shelly or the sanded, in attenuated and in 
distended individuals, and in specimens with symmetrical or 
non- symmetrical, or with two- or three-sided shells. 
The aperture of Miliola is round, oval, or square, accord- 
ing to the shape of the chamber ; and has in it a tongue-like 
process of shell-substance, which also varies in shape in 
different varieties, being often forked (in Spiroloculina), 
crescentic (in Quinqueloculina), and oblong (in Biloculina) : 
it acts as a partial septum between the chambers. In a 
Quinqueloculina abundant in the Tertiaries of Grignon, this 
plate becomes developed into a perforated septum, similar to 
what is a constant character in Hauerina, Fabularia, Pene- 
roplis, &c. 
Some of the Sph8eroidina3 and all the Yertebralinse are with- 
