LAGENIDA. 45 



set of forms, leading from the common round-based varieties towards the distomatons 

 series. 



These smooth apiculate Ln(/ence, or smooth subvarieties of L. caudata, D'Orb., are 

 found in many places in company with the common Lagence, and they are fossil in the 

 Tertiary strata. One or two small specimens only have occurred to us in the Crag of 

 Sutton. 



11. Lagena graciluma, Scguenza. Plate I, figs. 36, 37. 



MiLiOLA L.^vis, Ehrenberg (parte), 1845. Mikrogeol., part 2, p. 22, pi. 26, fig. 2. 

 Lagena i.-EVis, Parker and Jones, 1857. Aun. N. Hist., 2iid ser., vol. xix, p. 278, 



pi. 11, fig. 23. 

 Ampuorina acuminata, Seguema, 1862. Foram. Monotal. Mioc. Messin., p. 51, 

 pi. 1, fig. 35. 



CYLINDRACEA, Id. lb., fig. 36. 



— graciluma, Id. lb., fig. 37. 



— distorta, Id. lb., p. 52, pi. 1, fig. 38. 



Lagena sulcata, var. distoma-polita, Parker and Jones, 1865. Phil. Trans., vol. civ, 



p. 357, pi. 13, fig. 21 ; pi. 18, fig. 8. 



CharaderH. — Shell much elongated, fusiform, distomatons, often twisted or curved. 

 Both extremities subulate. Surface smooth. The hyaline texture of the young shell 

 becomes opaque white in older specimens. 

 Length j^th to ^th inch 



This may be regarded as the distomatons form, corresponding to L. lavis in the 

 single-mouthed series. Although it has been found elsewhere, both in recent and fossil 

 condition, we have never seen specimens approaching those from the Crag in point of size, 

 except from the Red Sea and Austraha ; indeed, those in Mr. Wood's collection from 

 Sutton are the largest Lagenm with which we are acquainted. 



Fig. 37, Plate I, represents a portion of the shell more highly magnified, and shows 

 very beautifully its foraminated structure. It may be constantly noticed, in examining 

 the shells of Lagena under high powers, that the amount of perforation varies with the 

 thickness of the wall ; that in the, thinner, more delicate portions the foramina are few and 

 indistinct, whilst in those places in which it assumes stouter proportions the surface 

 is closely studded with dots indicating the open ends of the tubuh. 



Distomatons Lagena are by no means common. The best-known form has an elon- 

 gated, straight-sided shell, Avitli delicate, parallel, longitudinal striae {Lagena distoma, P. 

 and J.), occasionally found in deepest soundings in the Northern Seas. 



Seguenza, in his ' Monografia dei Foraminiferi Monotalamici delle Marne Mioceniche 

 Messinesi,' figures four smooth-shelled double-mouthed specimens with as many different 

 specific names. Three of these are symmetrical, and one of them (fig. 37) the exact counter- 



