F. Chapman — Qauit Hyaline Foraminifera. 53 



are of classificatory rather than biological value: it being most 

 probable that the same organism may possess the ability to form the 

 structure of its external covering according to the conditions under 

 which the Ehizopod exists. 



Dr. Sollas has described^ two forms of Hyaline Foraminifera 

 from the Cambridge G-reensand under the generic term Webhina, 

 which presents the same finely perforated structure as the Gault 

 specimens, and he has proposed to reserve the generic term Wehbina 

 for the type he describes' possessing the perforate character. The 

 structure of the shell wall of these perforate varieties, as Dr. Sollas 

 points out, shows the type to be closely related to the Eotaline 

 Foraminifera : and since there is present a shelly flange which may 

 possibly be equivalent to the keel-like edge of some Pidvmulince, I 

 would therefore suggest that the perforate varieties of Wehbina 

 might form a separate genus, which would find a place between 

 Biipertia and Pulvinulma. 



Another somewhat remarkable form found is interesting on 

 account of the prominence which it gives to the fact of the great 

 variability of the Foraminifera. This is an adherent and ramifying 

 variety of Polymorphina. In general appearance it somewhat 

 resembles the form Sngenella of Dr. Brady, especially in the shape 

 of the terminations with their simple apertures. In a few specimens, 

 however, the portion of the test, which is rounded and inflated, and 

 is much smaller than the ramified portion, shows a decidedly 

 chambered structure, identical with that of PolymorpMna ; and this 

 is confirmed by one individual of which the test was broken, showing 

 the chambered portion. The cervicorn and fistulose varieties of 

 Polymorphina are very fully discussed in Messrs. Parker, Jones, 

 and Brady's paper on the genus Polymorphina ; ^ under the name of 

 Polymorphina Orbignii, Zborzewski, sp. 



Vitriwebbina, gen. nov. PI. II. 



General characters. — Test opaque to translucent, of a whitish or 

 pale-brown colour. Shell-wall very finely perforated. Consisting 

 of a single hemispherical or pyriform chamber, or of a graduated 

 series disposed usually in a curved line, and adherent upon some 

 foreign substance. The chambers are connected by stolon tubes, 

 very distinctly seen on the under surfaces of the specimens which 

 have become detached. The surface of the shell may be smooth, 

 pitted, or, as in Dr. Sollas's specimen, tuberculate. 



Vitriwebbina Sollasi, sp. nov. PI. II. Figs. 1-3. 



This form consists usually of one, but sometimes of even four 

 pyriform chambers, always adherent, in many cases to rolled 

 fragments of phosphatic nodules. The test is usually white, though 

 sometimes pale- brown and opaque, and the shell- wall is finely 

 tubulated, with the exception of a thin encircling flange of shell 

 material as it were completing the fusion of the shell to its attach- 

 ment. This peculiar flange of shell substance is present in Dr. 



1 Geol. Mag. Dec. II. Vol. IV. 1877, p. 102-105, PL VI. 



2 Trans. Linn. Soc. vol. xxvii. 1870 (1871), pL xlii. figs. 38 a—o, pp. 2il-2-18. 



