42 FORAMINIFERA OF THE CRAG. 



FissURiNA DiLATATA, Segueuza, 1862. For. Monot. Mioc. Jlessin., p. 6.5, pi. 2, fig. 21. 



lb., p. 66, pi. 2, figs. 22, 23. 



lb., fig. 2-1. 



lb., figs. 25, 26. 



lb., figs. 27, 28. 



lb., p. 67, pi. 2, fig. 29. 



lb., p. 68, pi. 2, figs. 36, 37. 



lb., p. 69, pi. 2, fig. 38. 



lb., fig. 39. 



lb., p. 70, pi. 2, fig. 45. 



lb., p. 71, pi. 2, fig. 46. 



lb., fig. 47. 



lb., figs. 48, 49. 



lb., fig. 50. 



lb. p. 73, pi. 2, figs. 52, 53. 

 Lagena marginata, £r(zc?y, 1864. Trans. Linn. Soc, vol. x.\iv. p. 472. 



— SULCATA, var. (Entosolenia) MARGINATA, P. and J., 1865. Phil. Trans., vol. 



civ, p. 355, pi. 13, figs. 42— 44 ; pi. 16, fig. 12 



Characters. — Shell orbicular, compressed, with a more or less prominent marginal 

 ridge or carina. Tube either Ectosolenian or Entosolenian. Aperture oval or slit-like. 

 Surface smooth. Colour white or dirty white. Length ^pth or less to ^th inch. 



Under the general name Lagena marginata are included a large number of flattened 

 forms, variable in shape, generally Entosolenian, but sometimes Ectosolenian with a long 

 delicate neck. This compressed shape is usually associated with a trenchant margin, 

 sometimes slightly apiculated, and sometimes dentate or rowelled (as in Williamson's 

 ' Monograph,' pi. 1, figs. 21 a, 25, 26), reminding us of the keel of certain CrisfeUaria. 

 Occasionally, in large well-developed specimens of L. marginata (recent and fossil) the 

 margin is composed of a large predominant rib, strengthened by a pair of smaller costae 

 [L.fasciata, Egger, &c.), showing that, as in other Foraminifera, especially the Nodosarine 

 group, the exogenous costae gather themselves to the margins, the rest of the surface 

 becoming less and less ornamented. The pseudopodial pores also usually affect the 

 neighbourhood of the thickened margin in these flattened forms, just as they follow the 

 ridges of L. striato-2nmctata. Occasionally the pseudopodia have perforated the whole 

 surface, either sparsely, or freely, as we have seen in specimens from the Indian Sea. 

 In some rare specimens from the Coral-reefs of Australia, and fossil at Bordeaux, we 

 see the pseudopodia begin to enter the shell-wall near the centre, and then burrow 

 radially to escape near the margin, the shell-surface being perfectly smooth and as 

 polished as glass (Z. radiato-marginata, P. & J.). 



The intussuscepted neck-tube in L. marginata is generally more or less oblique, 

 somewhat trumpet-shaped, and of varying length. The apparent difference in the 

 setting on of the mouth, which we formerly thought we could detect, between Entosolenia 

 and Lagena proper ('Annals Nat. Hist.,' 2nd ser., vol. xix, p. 279) does not really 



