KEPOKT ON THE FOE AMIN IEEBA. 
339 
Trochammina injiata is easily recognised by its large inflated segments and by tbe 
dark colour of its central chambers. It is one of the few species of Foraminifera that 
survive removal to brackish water, though the altered life-conditions bring about a corre- 
sponding change in the characters of the investment. In specimens living on the sea-bed 
the sandy walls of the test are compact and firmly cemented ; but those from 
brackish pools, whilst retaining the morphological characters of the type, have thinner 
walls, and the sand-grains are embedded in a chitinous envelope with scarcely any 
cementing material. The extreme modification in this direction is exemplified in 
Trochammina macrescens , in which the investment is a flexible membrane, with so little 
calcareous incrustation that it is scarcely altered by treatment with dilute acids. 
Trochammina injiata occurs at intervals all round the British Islands. It frequents 
comparatively shallow water, and finds its way into estuaries and other brackish areas. 
It has been collected by M. Berthelin on the north-east shores of the Bay of Biscay, and 
Mr. Robertson’s cabinet contains specimens from the south-east portion of the coast of 
Spain. 
It is found in the Post-tertiary clay of the Fens near Peterborough (Parker), and of 
the north-east of Ireland (Wright). Dr. Haeusler reports its occurrence in various beds 
of Jurassic age in the Canton Aargau, Switzerland. Tate and Blake include the species 
in their list of fossils from the Lias of Yorkshire, but the single figure they give ( loc . cit.), 
so far as it is distinctive at all, more nearly resembles Trochammina squamata than the 
present form. 
Trochammina nitida, PI. B. Brady (PI. XLI. figs. 5, 6). 
Trochammina nitida, Brady, 1881, Quart. Journ. Micr. Sci., vol. xxi., N. S., p. 52. 
„ ,, Id. 1881, Denkschr. d. k. Akad. Wiss. Wien, vol. xliii. p. 100, No. 25. 
Test free, regular, Rotaliform, compressed ; consisting of about three convolutions, 
the outermost of which has about nine segments. Superior face nearly flat ; inferior 
convex, somewhat excavated at the umbilicus ; peripheral edge rounded, only slightly 
depressed at the sutures ; aperture a curved slit on the final segment, close to the margin 
of the previous convolution. Surface smooth, not polished; colour greyish-brown. 
Diameter, -^th inch (0 '5 mm.). 
This is a comparatively rare species, but easily identified by the complanate superior 
surface of the test, and its even margin, as well as by the number and regularity of the 
chambers. It may be distinguished from its isomorph of the Lituoline series, 
Haplophragmium nanum, which is found in similar localities, by its more symmetrical 
contour and larger number of segments, and by the finer texture of its walls. 
Trochammina nitida was found in the northernmost area explored on the Austro- 
