REPOET ON THE FORAMINIFERA. 
441 
undivided chamber with a terminal aperture, or in exceptional cases with two apertures, 
and the walls are calcareous and finely perforated. These characters, simple as they 
appear, are compatible with an exceedingly wide range of variation in minor particulars, 
chiefly in relation to — (1) the shape of the test ; (2) the nature of the aperture ; and (3) the 
condition of the exterior with reference to surface-ornament. 
The general contour of the shell may be subglobular or pyriform, as in Lagena 
globosa, ovate as in Lagena ovum, obovate as in Lagena ovata, truncate at the base- as in 
Fig. 11. — Various forms of aperture in Lagena globosa. Magnified 120 diameters. 
a. 
b. 
c. 
a-g. Oral aspect of the shell, showing the external orifice. 
Rounded orifice in a slight depression. 
Oval orifice with raised border. 
Simple elongated fissure. 
d. Bordered fissure. 
e. Triradiate fissure, with border. 
f. g. Stellate orifices. 
/ 
h-m. Lateral aspect of similar shells. 
h. Specimen similar to a, showing the entosolenian tube. 
i. Fissurine form like d, the internal tube hidden by the thickness of the shell. 
j. Specimen with stellate orifice. 
k. l. Entosolenian specimens with rough external necks, apparently of the same character as the fistular shelly growths of the 
Polymorphince. 
m. Specimen with external (ectosolenian) neck at one end and internal tube at the other. 
Lagena truncata, flask-shaped as in Lagena Icevis, decanter-shaped as in Lagena cvenata, 
cylindrical and curved as in Lagena botelliformis, fusiform as in Lagena gracillima, 
or elongate and tubular as in Lagena elongata ; and many of these forms have correspond- 
ing flattened varieties, as well as others which are polygonal in outline, in addition to 
numerous modifications dependent to a greater or less degree upon supplementary or 
exogenous growths. The test is almost invariably equilateral, or in the polygonal 
varieties symmetrical ; and this is so constant a rule that any irregularity of outline may 
be treated as the result of accident, or as due in some way to external conditions. 
