POLYMORPHINA THOUINI. 261 



A somewhat indefinite biserial arrangement, in which the segments appear 

 irregularly opposed to each other rather than in alternation, together with the 

 rounded mai'gins and constricted septa, are characters sufficient for general 

 diagnosis. The difficulty in distinguishing attenuated specimens from those of 

 P. cylindroides is confessedly great ; but the less compressed contour of the latter, 

 its few chambers, and their erect position, will usually serve the purposes of the 

 systematist. 



A specimen of irregular growth is shown by fig. 26, PI, V. It is so much 

 encrusted with carbonate of lime that it presents a false resemblance to P. variata. 



Occurrence. — Polijmorphina compressa has a wide range, but is most common in 

 the comparatively shallow waters of temperate latitudes. It has been found as 

 far north as Smith Sound and Novaya Zemlya; also in the tropical South 

 Atlantic and the North and South Pacific. It mostly aifects shallow water, but 

 specimens have been found at depths of from 400 to 600 fathoms. 



In the fossil condition P. compressa has been recorded from the Lower and 

 Middle Lias of the north part of France, and from the Middle and Upper Lias of 

 Somerset. It has been found also in the Lower Oolite of Somerset ; in the Oxford 

 and Kiraeridge Clays ; in the Cretaceous of England, France, Germany, and 

 North America. We have not observed any records from Eocene deposits ; but 

 it has been recorded from the Oligocene of Germany, from the Miocene of 

 Vienna and Muddy Creek (Victoria), from the Pliocene of Belgium and St. Erth, 

 and from the Pleistocene of Norway and the West of Scotland. In the Crag we 

 have met with it in every zone examined. 



6. PoLYMORPHiNA Thouini, cV Orhlgnij, 1826. Plate I, fig. 59, 



PoLTMOEPniNA Thouixi, d'Orb., 1826. Add. Sci. Nat., vol. vii, p. 265, No. 8, 



Module, No. 23. 

 BiGENEEijfA Ceet^, Ehrenhevff, 185-1. Mikrogeologie, pi. xxviii, fig. 21. 



— ACANTHOPHOEA, Ehretilerg, 1854. Ibid., pi. xxviii, fig. 22. 

 Peoeopoeus Ceet^, Elirenherg , 1854. Ibid., pi. xxvii, fig, 29; and pi. xxviii, 



fig, 20. 



— sicuLus, TShrenherg, 1854. Ibid., pi. xxvi, fig. 18. 

 PoLTMOEPHiNA PUPiFOEMis, Terquem, 1864. Poram. Lias, 4e Mem., p. 300, 



pi, xiii, figs. 23, &e. 



— Thotjin-i, p., J., and B., 1865. Ann. Mag. Nat. Hist., ser. 3, 



vol. xvi, p. 22, pi. ii, fig. 49. 



— — J"., P., a«c? B.,18G6. Monogr. Foram. Crag, App. I and 



II, Tables, No. 50, pi. i, fig. 59. 



— — B., P., and J., 1870. Trans. Linn. Soc, vol. xxvii, 



p. 232, pi. xl, fig. 17. 



