68 FORAMINIFERA OF THE CRAG. 



shell. We have never seen it so abundant as in some sands dredged in from thirty to 

 forty fathoms, in Berwick Bay, and in that locality the finely grown Vaffinulince were 

 found to be almost without exception in the ribbed condition. It is impossible to dis- 

 tinguish the smooth, slender, depauperated forms of Vaginulina from Dentalina communis; 

 indeed, the two varieties merge insensibly into each other, whilst the costulate Vaginidince 

 are barely separable from B. obliquestriafa. 



V. linearis is not uncommon in a recent condition on our own shores, though it 

 appears to be somewhat local in its distribution, and the same remark applies to its 

 occurrence in seas of both colder and warmer latitudes. 



In a fossil state it is less common, but it is occasionally met w'ith in beds belonging 

 to the Secondary and Tertiary periods. 



Subgenus — Margimulina, 2)' Orh'ignij. 



Nautilus, Orthoceras, Orthocera, Cristellaria, Ortiiocerina, 



Hemicristellaria, Auctorum. 

 Makginulina, D'Orbiffny, Cornuel, Roerner, Reuss, Neuegehoreti, 



Bornemann, Parker, Jones, Brady, Terquem, Karrer, Costa, ^-c. 



Characters. — Shell elongated, subcylindrical or flattened, straight or arcuate, tending 

 to spiral mode of growth in the earlier chambers ; ornamented with ribs, granules, spines, 

 &c., as other Nodosarince. Aperture nearly always excentric towards or close to the 

 convex margin of the shell. 



The difficulty of defining any special groups among the Marginuline NodosarincB is 

 insuperable, every character being variable, namely, the excentricity of the axis of the shell 

 (whether amounting to spirality or simply to a curvature), the compression, and the orna- 

 mentation, which last has the same patterns as in other NodosarincB. 



We may take the simple smooth Margmdinoe as one group ; but we are baffled by the 

 ever-varying proportions and shape among them ; and, hesitating to adopt a name for 

 every individual, we are obhged to take M. glabra (see further on) as a subtype, though 

 it graduates in form into Vaginulina, Dentalina, and Nodosaria, on one hand, and into 

 Cristellaria on the other ; whilst, as to ornament, it takes on more or less of the exogenous 

 shell-growth, thus becoming any one of the hispid, costate, limbate, or otherwise orna- 

 mented varieties. 



For another subtype in our artificial grouping, we may take the ribbed 31. raphanus, 

 to be presently described. For another, the keeled forms J/, carinata, D'Orb.,^ and M. 

 angistoma, Stache,' may serve. A fourth group may comprise the limbate varieties, either 



1 'Ann. Sc. Nat.,' vol. vii, p. 259, No. 8. - ' Novara-E.xped.,' &c., pi. 22, %. 46. 



