from the a Cambridge Greensand. 



315 



This species was first recorded from the Gault. It has 

 since been found in the Middle Marl of New Jersey and in 

 the lowest beds of the Chalk. 



Vitriivebbina tuberculata (Sollas). (Fig. 3.) 



Webbina tuberculata, Sollas, 1877, Geol. Mag 1 , dec. ii. vol. iv. p. 104, 



pi. vi. figs. 4-7 & 9. 

 Trochammina irregularis (d'Orbigny), Perner, Ceska Ak. Cisai-e 



Frantiska Josefa, Prague (Palasont. Bohemias, no. 1), p. 53, pi. ix. 



figs. 1-6. 

 Vitrhvebbina tuberculata (Sollas), Chapman, 1896, Ann. & Mag. Nat. 



Hist. vol. xviii. p. 332, fig. 4 ; id. 1896, Journ. R. Micr. Soc. pp. 586, 



587, pi. xiii. fig. 3. l 



By far the finest specimen of this form I have met with is 

 here figured from the Cambridge Greensand of S waff ham 

 (fig. 3). It is remarkable for having no less than ten 



Fig. 3. 



Vitriwebbina tuberculata (Sollas). X 15. 

 p= primordial segment. 



segments, and by its completeness throws considerable light 

 on one of the methods of its growth. Vitriwebbina is more 

 usually found as a series of chambers of gradually increasing 

 size ; but the specimen before us gives an instance of a 

 deviation from this general habit. The primordial segment 

 in this specimen immediately gives rise to a double series of 

 chambers of about equal dimensions extended laterally on 

 either side of the commencement. This specimen is attached 

 to a brown (?) fish-bone fragment. 



Originally described from the Cambridge Greensand, this 

 species has since been found in the Gault of Merstham and 

 Folkestone and in the Cenomanian and Chalk of Bohemia. 

 Six specimens of Vitriwebbina tuberculata occur in this 

 present series from the Cambridge Greensand of Swaffham. 



