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THE VOYAGE OF H.M.S. CHALLENGER. 
room for doubt. In a few species of Miliolina the exterior is punctate or pitted ( Miliolina 
rupertiana, PI. VII. figs. 7-12, and in certain fossils, e.g., Miliolina saxorum ) ; but thin 
sections of the test show conclusively that the perforate appearance is due to superficial 
depressions of uniform depth, only penetrating about half the thickness of the shell-wall. 
Similar punctations may be observed in the genera Peneroplis and Orbiculina (PI. XIII. 
fig. 23, and PL XIV. fig. 13), sometimes occurring on the exterior and sometimes on the 
interior surface of the test, but their superficial character has been fully demonstrated by 
Dr. Carpenter. 1 
The inter-relationship of the various generic types of the Miliolidce is easily traced. 
The sub-family Nubecularina comprises only a few simple and very variable forms, which 
in some respects stand apart from the rest of the group. The test of Squamulina consists 
of a single adherent chamber, with an aperture on the convex surface ; whilst the poly- 
thalamous Nubecularia is connected with Peneroplis by its more regular spiral forms, and 
with Miliolina by its least regular free varieties. 
But for the remainder of the Family, the genus Cornuspira, the test of which consists 
of a non-septate tube coiled in one plane, may be taken as the starting-point. A shell hke 
that of Cornuspira, with constrictions at two opposite points of each convolution, that is 
to say, with each convolution divided into two segments, is the type of the genus Spiro- 
loculina, and from this the other strictly Milioline genera differ chiefly in such particulars 
as the mutual disposition of the segments, their obliquity and degree of curvature, and the 
extent to which they overlap each other. The genus Fabularia, morphologically speak- 
ing, is a Biloculine Miliola with labyrinthic chambers. 
The Hauerinina constitute a group of dimorphous forms connecting the Miliolinina 
with the Peneroplidina. The sub-family is best represented by the genus Hauerina, 
which, except in its very early growth, may be described as a Cornuspira or Spiroloculina 
with more than two segments in each convolution ; and the closely allied Planispirina is 
essentially a Hauerina with the chamber-walls spreading over the lateral faces of the test 
in Nummuline fashion. 
The genus Peneroplis, like Cornuspira, is spiral from the commencement, and each 
convolution is divided into many segments. The spire is either nautiloid or explanate, 
and the later chambers often diverge in a straight, linear series. Orbiculina resembles 
the spiral Peneroplides, but has its chambers subdivided into chamberlets, and in this 
particular forms the connecting link with Orbitolites. The simpler varieties of Orbitolites 
begin spirally, the more complex usually commence with a large primordial chamber ; 
but both almost immediately assume a cyclical plan of growth, and the mature shell 
consists of a large number of annular chambers, each divided into numerous chamberlets. 
Alveolina has a spiral test, more or less elongated on the axis of convolution, and the 
chambers subdivided into chamberlets. From a morphological point of view it is an 
1 Phil . Trans ., 1856, p. 551 ; ibid ., 1858, p. 4. 
