558 
THE YOYAGE OF H.M.S. CHALLENGER. 
two, three, or more ; and also on their more or less embracing character, and the degree 
to which they are separated by the depression or excavation of the sutures. These sub- 
generic terms have been employed, with or without reservation, by most Continental 
writers, but they are at last falling into disuse, as it is found that they do not really 
facilitate the systematic treatment of the group, but rather the reverse. They are, 
however, of certain interest as indicating the principal lines of structural variation and 
the resulting modifications in external form. Thus the Pyruline and Globuline series 
have nearly regular Lagena-\\k.Q tests with complanate sutures ; the Guttuline forms have 
inflated segments, of which a larger number are visible, combined in a somewhat obscure 
triserial spire ; whilst the modifications of Polymorphina , proper, range from the 
irregularly triserial to the biserial varieties, of which some of the latter approach Textularia 
itself in the symmetrical disposition of their segments. 
The aperture of the test is placed near the centre of the distal end of the final segment, 
either even with the surface or in a mammillate protuberance. The orifice consists 
sometimes of a number of radiating fissures, sometimes of a round opening encircled by a 
collar of radiating grooves or of slightly raised lines. In exceptional cases it is found 
in the form of a circular, oval, or fissurine opening, without the radiating border ; and 
occasionally it is subdivided into a number of small pores. In one somewhat anomalous 
species, Polymorphina longicollis, the nipple-like projection is developed into a tubular 
neck of some length, terminating in a phialine or radiate lip ; and specimens are by no 
means rare, especially in the starved or poorly developed varieties, in which the aperture 
forms an entosolenian tube extending into the cavity of the final segment. 
The exterior of the test is either smooth, or beset with setae, spines, or tubercles, or 
with granular lines, parallel striae, or raised costae. 
In one peculiarity the genus Polymorphina stands almost alone amongst Forami- 
nifera, namely, the tendency displayed by the later segments to produce irregular 
fistulose outgrowths, as shown in PI. LXXIII. figs. 14-17. These expansions are 
probably an evidence of redundant growth, and they assume a great diversity of aspect. 
The shelly investment is commonly very thin, and often rugose externally ; the 
margins are extended into tubular and sometimes irregularly-branching processes, the 
open ends of which serve as orifices. Soldani devotes three entire plates of the 
Testaceographia to the illustration of these curious anomalous forms. The fistulose 
or cervicorn varieties have been treated by some writers as constituting collectively a 
distinct specific or even generic 1 group; but as almost all the commoner species of Polymor- 
phina are found from time to time in this condition, it appears more natural to assign 
such modifications to their respective types, their true position being that of individuals 
of monstrous development. Prof. Eeuss in his later works adopted the latter view, and 
it has been followed in the present Report. 
1 The genus Aulostomella of Altli, see Haidinger’s Naturw. Abhandl., 1850, vol. iii. p. 263. 
