REPORT ON THE EORAMINIFERA. 
317 
composed of several convex chambers, either connected by short stoloniferous passages or 
crowded one against the other ; margins rounded or lobulate, with simple or forked 
tubular extensions which form the pseudopodial apertures. 
In Placopsilina vesicularis the segments are characterised by their inequality of size 
and shape, and their irregular combination. In these particulars it differs from 
Placopsilina cenomanci, in wdiich the chambers are of more even dimensions, and are 
combined in single linear series. Monothalamous specimens are less convex than 
Placopsilina bulla, and generally have several peripheral orifices, as shown in fig. 19. 
With the exception of a single locality in the South Atlantic east of Buenos Ayres, 
1900 fathoms, -where the ground is extremely rich in arenaceous Rhizopods, Placopsilina 
vesicularis has only been obtained from dredgings taken on the first cruise of the 
“ Porcupine,” between the north-west of Ireland and the Rockall Bank. It occurs at 
three Stations in this region, at depths of 630 fathoms, 1215 fathoms, and 1443 fathoms 
respectively. 
Ilaplostiche, Reuss. 
Noclosaria, pars, d’Orbigny [1826]. 
Lituola, pars, Jones and Parker [1860], Carpenter, Yanden Broeck, Brady. 
Haplostiche, Reuss [1861], Brady, Seguenza, Biitscldi. 
Test free, coarsely arenaceous ; composed of a number of segments joined together 
in a straight or curved (never spiral) series. Chambers labyrinthic. Aperture terminal ; 
porous or dendritic, rarely simple. 
Although in the original description of the genus Ilaplostiche prominence is given 
to the subdivision of the chambers by secondary septa, and to the variable nature 
of the aperture, the term was in reality made use of by Reuss for all the Nodosariform 
Lituolince ; and neither in his essay on classification , 1 nor in his final arrangement of the 
Lituolidea 2 did the author provide for the linear forms which have simple chamber- 
cavities. The oversight is no doubt due to the fact that the arenaceous types were 
studied chiefly from fossil specimens, and that chambers filled by mineral infiltration 
were not always in a state in which the characters of the interior could be properly 
determined. Arenaceous isomorphs of the Nodosariae are altogether less common in the 
fossil than in the recent condition, if we may judge by the comparatively small 
number of species that have hitherto been described ; but it is possible that the pro- 
portion of labyrinthic to simple types may be relatively larger. It cannot be stated 
with any certainty whether all Reuss’s species of Ilaplostiche accord with the characters 
1 Sitzungsb. d. 7c. Ah. Wiss. Wien, 1861, vol. xliv. p. 381. 
- Das Elbthalgebirge in Sachsen, 2 ter Tli., 1874, p. 119. 
(zOOL. CUALL. EXP. — PART XXII. — 1883b 
Y 41 
