EOEAMINIFEEA EEOM THE NOETH ATLANTIC AND AECTIC OCEANS. 
359 
described (as Oolince ) by D’Orbigny in his work on the Foraminifera of South America 
(Voyage dans l’Amer. Merid. partie 5 me , 1839, p. 20). These represent most of the 
modifications shown among the Arctic and North Atlantic forms. Thus 
Oolina inornata, op. cit. pi. 5. fig. 13 = Lagena globosa, Montagu. 
lasvigata, ,, 
fig. 3 = L. lee vis, Montagu. 
striatocollis, „ 
fig. 14 = L. semistriata, Williamson. 
striata, „ 
fig. 12 
Vilardeboana, „ 
figs. 4, 5 s 
Isabella, „ 
figs. 7, 8 ' = L. sulcata, Walker and Jacob. 
rarieosta, ,, 
figs. 10, 11 J 
Melo, „ 
fig. 9 
compressa, „ 
figs. 1, 2 = L. marginata, Montagu. 
caudata, „ 
fig. 6 
Genus Polymorphina. 
Polymorphina lactea , Walker and Jacob, sp. Plate XIII. figs. 45, 46 (Arctic). 
Of the hyaline Foraminifera, Polymorphina alone forms itself persistently of a double 
row of alternating opposite chambers ; except very rarely, when its latest chambers are 
uniserial ( Pimorphina ). TJvigerina (a closely related form) has normally three chambers 
in one turn of the spire, forming a triple series of alternating chambers. Teoctularia 
has normally a double series of chambers alternating with each other, much as in Poly- 
morphina , but more regular in arrangement, and having a far more gradual increase of 
size. Textularia, however, often begins with a triserial (Verneuiline) arrangement, such 
as is normal in TJvigerina ; and, like the latter, it often finishes its shell with a single 
row of chambers ( Bigenerina ). 
In Polymorpliina , although the arrangement of the chambers is essentially biserial, 
yet they are very apt to grow so loosely that a cross section through the shell will often 
expose three or more chambers. 
This shell is normally drop-shaped, tear-shaped, and pyriform ; it may, however, 
become flattened out into the proportions of the thick leaf of a succulent plant, or be 
elongated into an irregular oblong, somewhat like a wheat-ear or grass-spike. These 
longer forms (such as fig. 48) are isomorphic with Textularia proper. Of its Dimor- 
phine condition there are Nodosarian, Textularian, and Uvigerine isomorphs. 
The aperture of Polymorphina agrees with that of the Nodosarince , and of the well- 
grown Lagence (such as figs. 30 & 31), being radiated or plicated, the sarcode passing 
through a circular series of slits. The actual centre of the aperture is sometimes filled 
up with a bead of calcareous matter (fig. 52 h), and this occurs in Nodosarince also. 
W e have seen above that the varieties of Lagence are almost equally divided among 
those which have a gently graduating external neck, those having an entirely internal 
neck-tube, and those in which the tube is partly extruded and partly internal. In Poly- 
morphina also this may be said to hold good to some extent ; for in small and in young 
specimens (fig. 46) we see the Entosolenian tube, just as in the globular and flat Lagence 
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