CRISTELLARIA GIBBA. 247 



mencing with the Silurian ; ^ it is represented in the Lias and Oolite, and abounds 

 in the Gault, Chalk-marl, and Chalk. Together with cognate forms or varieties, 

 it is plentiful in many Tertiary deposits at home and abroad. Recent specimens 

 are not very common, but have been found in Arctic, Atlantic, and North-Pacific 

 dredgings at considerable depths, and in the Mediterranean and Adriatic Seas. 

 In the Crag it is very rare, one or two smallish specimens from Sutton, and 

 Thorpe, near Norwich, in Mr. Wood's Collection, being the only reliable examples 

 we have seen. 



Together with its ally, G. rotulata, this Cristeilaria is widely diffused in seas 

 and oceans, as far north as the Arctic Circle on the coast of Norway, and down 

 south on the shores of Patagonia. Fine specimens are rarely found at less 

 depth than 100 fathoms. C. cuUrata was collected by the 'Challenger' in the 

 North Atlantic at from 390 to 2435 fathoms ; in the South Atlantic at 350 and 

 675 fathoms ; in the South Pacific from 38 to 275 fathoms ; and in the North 

 Pacific at 95 fathoms. It lives also in the Mediterranean and Adriatic. Small 

 specimens with narrow keel occur in shallow water in the British seas. 



2. Cristellaria gibba, d'Orbigny. Plate VII, figs. 19 a, h. 



Ceistellabia gibba, d'Oi-b., 1826. Ann. Sci, Nat., vol. vii, p. 292, No. 17. 



— — Idem, 1839. Foram. Cuba, p. 40, pi. vii, figs. 20, 21. 



^- EXCiSA, Bornemann, 1855. Zeitsch. Deutsch. Greol. G-es., vol. vii, 



p. 328, pi. xiii, fig. 19. 



— NUDA, Beuss, 1861. Sitzungsb. k. Akad. Wiss. Wien, vol. xliv, 



p. 328, pi. vi, figs. 1—3. 



— PULCHELLA, Idem, 1862. Ibid., vol. xlvi, p. 71, pi. viii, fig. 1. 

 EoBULiNA coNCiNNA, Idem, 1863. Ibid., vol. xlviii, p. 52, pi. v, fig. 58. 

 Ceistellabia gibba, Brady, 1884. Eeport ' Challenger,' p. 546, pi. Ixix, figs. 8, 9. 



— — Burrows, Skerhorn, and Bailey, 1890. Journ. Roy. Micr. Soc, 



p. 559, pi. X, figs. 19 a, h, 21. 



— — Orick and Sherborn, 1891. Journ. Northampt. Nat. Hist. 



Soc, vol. vi, p. 212, pi. vi, fig. 29. 



— — Chapman, 1896. Journ. Eoy. Micr. Soc. for 1896, p. 4, 



pi. i, figs. 7 a, h. 



Characters. — This small subovate form is one of the many intermediate to 

 the closely coiled Cristellaria rotulata and the more expanded and elongate 



1 Cristellaria rotulata {?), Schlumberger, ' Journ. Cincinnati Soc. Nat. Hist.,' vol. v, 1882, 

 p. 119, pi. V, figs. 2, 2 a. Cristellaria, sp., Terquem, is found in the Devonian, ' Bullet. Soc. Geol. 

 France,' ser. 3, vol. viii, 1880, p. 418, pi. xi, fig. 8. 



