F0RAMIN1FERA FROM THE NORTH ATLANTIC AND ARCTIC OCEANS. 403 
less feeble Nautiloid forms make advances towards the true Polystomellan characteristics ; 
thus showing that they certainly are within one and the same specific limits ; moreover, 
the next variety, N. Scapha, is seldom quite free from bridges across the divisions of its 
chambers on each spiral lamina, as may be seen in figs. 37 and 38, Plate XIV. 
Polystomella crisp a, Linn., sp., Var. ( Nonionina ) asterizans , Fichtel and Moll, sp. Plate 
XIV. fig. 35 (Arctic) ; Plate XVII. figs. 54 a, 54 b (North Atlantic). 
This is a small, many-chambered, Nautiloid Nonionina , somewhat variable in its 
features, but having a slight umbilical growth of exogenous shell-matter often radiating 
along the septal furrows for some distance. This star-like limbation is much exaggerated 
in N. Limba , D’Orb. (Modeles, No. II), and curiously modified with flaps in N. stelligera, 
D’Orb. (For. Canar. pi. 3. figs. 1, 2). N. asterizans varies as to its granulations and 
stellate umbo, readily passing into N. granosa and into N. stelligera. Fig. 35 is of a 
stronger make than the latter, and is such as frequents deeper water than that does. It 
is from the Hunde Islands (Sutherland’s dredgings) at from 25 to 30 fathoms, where 
it is common but small. N. asterizans is common in the British seas in shallow water. 
Plate XVII. fig. 54 differs from the Arctic specimen as to the umbo, but is not sepa- 
rable. It is from 740 fathoms north of Newfoundland Bank. 
The tribe of small Nonionince converging round Nonionina asterizans , although con- 
veniently considered as a subspecific group, yet in reality are essentially of the same 
specific type as that to which Polystomella crispa belongs. They may be said to present 
arrested or feebly developed conditions of the form in which, under other circumstances, 
a luxuriant growth of exogenous shell-matter symmetrically bridges over the septal lines, 
and otherwise thickens and ornaments the shell. Nonionina Limba , D’Orb., belongs to 
this group, and is very apt to take on the characters of the type in connexion with its 
own, and thus to pass insensibly into it. It is a Tertiary form, at Grignon, Bordeaux, &c. 
Polystomella crispa , Linn., sp., Var. ( Nonionina ) depressula, Walker and Jacob, sp. Plate 
XIV. figs. 39 a , 39 b (Arctic). 
This is a delicate feeble form of Nonionina asterizans , Fichtel and Moll, sp., with the 
stellation of the umbilici imperfect. 
It is common in the shallow sea-zone and in. the brackish water of river-mouths and 
salt-marshes of the British area ; and is the commonest shell in the clay of our Eastern 
Counties fen-district, excepting at the margin of that sub-recent deposit, for there Tro- 
chammina inflata attains its highest development and abounds most. This form is very 
apt to turn up, all the world over, in such shallow water as is rendered somewhat unfit 
for rhizopodal life by the presence of large quantities of earthy or vegetable matter,- — 
for instance, in bays, harbours, estuaries, &c. 
We have it from the Hunde Islands (Sutherland’s dredgings) common and small at 
from 25 to 30 and 50 to 70 fathoms ; common and middle-sized at from 60 to 70 fathoms. 
