Lhetic Foraminifera from Somerset. 317 
follows :—“ Test free, convoluted, discoidal, thin, consisting 
of a spuriously septate tube coiled in one plane. Septa 
marked externally by oblique slightly depressed lines. 
Diameter 75 inch (‘4 millim.).” 
This species was regarded by Brady as a transitional form 
between A. cncertus and the septate ‘Trochammine of the 
type 7. inflata. Since the arenaceous tube is not definitely 
septate, the species is here placed in the genus Ammodiscus. 
In the Rheetic specimens the peripheral edge of the test is 
somewhat sharper than that of the Carboniferous examples, 
and its diameter averages 7's inch (0°34 millim.). 
The occurrence of A. anceps in beds of Rhetic age is of 
exceptional interest, seeing that it was described by Dr. Brady 
from the Carboniferous rocks of Hngland and Scotland, and 
was there very rarely met with. I have since found this 
form in the Upper Lias of Northampton. 
Found in bed no. 2 of the Rheetic series at Wedmore, 
very common. 
9. Ammodiscus centrifugus (Brady). 
(rie x ties Te) 
Trochammina centrifuga, Brady, 1873, Mem. Geol. Survey Scotland, 
Expl. Sheet 23, p. 95; id. 1873 (in Young and Armstrong's Catal.), 
Trans. Geol. Soc. Glasgow, vol. iv. p. 271; id. 1876, Monogr. of 
Carb. and Perm. Foram. (Pal. Soc.) p. 74, pl. ii. figs. 15-20. 
This form is probably only a variety of A. ¢ncertus, as was 
suggested by Dr. Brady, the only difference consisting in the 
straight extension of the last turn of the coiled shell. The 
Rhetic specimens have the surface of the test much 
wrinkled. 
A. centrifugus was found in the Lower Carboniferous 
Limestone of England and Scotland, at which horizon it 
occurred rarely, and in the Upper Carboniferous Limestone of 
both countries frequently. One or two examples, probably 
referable to this form, have also occurred in washings of Upper 
Lias clay from Northampton. 
This species occurs in the Rhetic series of Wedmore in 
bed no. 2, where it is rare. 
10. Ammodiscus milioloides (Jones, Parker, and Kirkby). 
(Pl. XI. figs. 12, 13.) 
Trochanmuna milioloides, J., P., & K., 1869, Ann. & Mae. Nat. Hist. 
ser. 4, vol. iv. p. 390, pl. xiii. figs. 9-14; Brady, 1876, Monogr, 
Carb. and Perm. Foram. (Pal. Soc.) p. 79, pl. iii. figs, 11-15. 
This species was hitherto essentially Permian, found in the 
