260 Dr. R. L. Sherlock — Foraminifera of Speeton Clay. 



Vaginulina, d'Orbigny. 



Vaginulina ineompta{?), Keuss. (PI. XIX, Fig. 10.) 



Vaginulina incom'pta, Eeuss, 1862 : Sitzungsb. d. k. Ak. Wiss. Wien, vol. xlvi, 

 p. 45, pi. iii, fig. 5. 



RemarJcs. — One specimen probably belongs to this species. The 

 initial cell is rather small and the chambers are somewhat more 

 obliquely set than in E,euss' figure. He describes it as very rare in 

 the Upper Hils Clay at Gliickauf. 



Sorizon. — Found in Upper C2. One specimen. 



Fragments of other species of Vaginulina have been found in 

 B base c, Upper C2, and Dg mid, but too imperfect for specific 

 determination. 



Cristellaria, Lamarck. 



Cristellaria graeillissima, lieuss. (PI. XVIII, Fig. 26.) 



Cristellaria graeillissima, Keuss, 1862 : Sitzungsb. d. k. Ak. Wiss. Wien, 

 vol. xlvi, p. 64, pi. vi, figs. 9, 10. 



Remarks. — The specimens vary greatly in length and the extent to 

 which the spiral part is developed ; some have scarcely any spiral 

 commencement and are very close to C. fceda, Reuss (op. cit., p. 64, 

 pi. vi, figs. 11-13). There can be little doubt that the two forms are 

 really one species, and that foeda should be dropped as a specific 

 name. It is possible that the form figured by G. R. Vine from the 

 Cambridge Greensaud as ? Troehammina helvetico-jurassica, Hausler 

 (Proc. Yorks. Geol. Polytech. Soc, n.s., vol. ix, pt. i, p. 28, pi. ii, 

 fig. 16, 1885 (1886)), is C. graeillissima. There is a resemblance in 

 the outline of the shell and the mouth, and C. graeillissima in some 

 cases appears to have an arenaceous test, owing to the rough prickly 

 surface. The small side-chamber in Vine's figure is, however, very 

 difficult to account for on this hypothesis. 



Viewed as a transparent object, the rough surface of C. graeillissima 

 is seen to be due to the outgrowths of calcite in optical continuity 

 with the shell. 



Horizon. — Common in B base c. 



Cristellaria acutauricularis (Fichtel & Moll). (PI. XIX, Fig. 2.) 



Nautilus acutauricularis, Fichtel & Moll, 1803 : Test. Micr., p. 102, pi. xviii, 



figs. g-i. 

 Cristellaria polita, Eeuss, 1855 : Sitzungsb. d. k. Ak. Wiss. Wien, vol. xviii, 



p. 237, pi. iii, fig. 41. 

 G. acutauricularis, Brady, 1884: Chall. Eep., vol. ix, p. 543, pi. cxiv, 



figs. 17a, b. 



Remarks. — The Cristellarians are (with the exception ol Pulvinulina 

 caracolld) the commonest of all the Foraminifera in the Speeton Clay, 

 and offer great difficulties in specific determination, since no two 

 specimens are quite alike and the number of described species is very 

 great. Figures of the same species given by different authorities 

 differ widely. A number of specimens seem certainly referable to 

 C. acutauricularis, whose range in time extends at least as far back 

 as the Lias. The species has been recorded from that formation by 



