REPORT ON THE FORAMINIFERA. 
S3 7 
bilaterally symmetrical, as in Trochammina trullissatci, Rotaliform as in Trochammina 
infiata, trochoid as in Trochammina squamatci, or altogether irregular as in Trochammina 
conglobcita. They are, with but little exception, free-growing ; if adherent, the test is 
complete, and not tent-like without a proper shell on its inferior side, as in Webbina. 1 
The segmentation is generally as perfect as that of the hyaline types of Foraminifera. 
The walls of the test are thin, and smooth externally ; usually the interior surface is also 
smooth, but sometimes it is punctate or otherwise superficially marked. The aperture is 
invariably simple and undivided, and commonly takes the form of an arched slit. 
The genus is cosmopolitan, both in its geographical and bathymetrical relations, 
though the individual species have a tolerably well-defined range of depth. Its earliest 
appearance, geologically speaking, is in the Lower Lias ; but in the fossil condition 
Trochammina (proper) occurs much less frequently than the non-septate type Ammodiscus, 
and the number of specimens hitherto found is comparatively small. 
Trochammina squamata, Jones and Parker (PL XLI. fig. 3, a.-c.). 
Trochammina squamata, Jones and Parker, 1860, Quart. Journ. Geol. Soc., vol. xvi. p. 304. 
„ „ Carpenter, 1862, Introd. Foram., p. 141, pi. xi. fig. 1. 
,, jproteus (pars), Karrer, 1865, Sitzungsb. d. k. Ak. Wiss. Wien, vol. lii. p. 494. 
pi. i. fig. 6. 
„ squamata , Brady, 1879, Quart. Journ. Micr. Sci., vol. xix., N. S., p. 56. 
Test free or adherent, trochoid, Rotaliform ; consisting of about four convolutions, 
each composed of four or five chambers ; superior face convex or subconical ; inferior flat 
or slightly concave ; aperture an arched slit near the margin of the final segment on its 
inferior side. Colour brown ; surface smooth, not polished. Diameter, about ^fli inch 
(0‘84 mm.). 
In establishing the genus Trochammina, Parker and Jones employed the specific 
term “ squamata ” for the form which they supposed to embody the typical characters 
of the group, and it is somewhat unfortunate that any doubt should have existed as to 
the precise variety they had in view. The only published figures to which the name has 
been appended are those in their “ North Atlantic ” memoir. 2 I have long suspected that 
these drawings represent the species previously described by Williamson under the 
name Rotalina ochracea , 3 and a recent examination of the type-specimens of the latter, 
kindly lent by the author, has convinced me that the supposition is well founded There 
is, however, an allied but quite distinct modification of the genus, for which the same 
1 I am not quite sure that this is invariably true of Trochammina ochracca ; occasional specimens appear as though 
the test had grown tent-wise, like Webbina. 
2 Phil. Trans., vol. civ., pi. xv. figs. 30, 31. 
3 Bee. For. Gt. Br., p. 55, pi. iv. fig. 112, pi. v. fig. 113. 
