38 DU. CAEPENTEE’S EESEAECHES ON THE EOEAAIINIFEEA. 
the chambers is here prolonged in an unusual manner over the borders of 
the septal plane: — 100 diam. 
Figs. 16, 17, 18, 19. Side and front views of young specimens oi Peneroplis, showmg 
various departures from the normal type in the form of the septal plane 
and in the disposition of the apertures : — 40 diam. (See also figs. 2, 6, 8, 9, 
10, 14.) _ . • 
Fig. 20. Portion of the ordinary surface of Peneroplis more highly magnified, showmg 
its ridge-and-furrow plication, and its rows of minute punctations. 100 
diam. _ , . 
Fig. 21. Portion of the ordinary surface of Dendritina, showing precisely similar 
characters: — 100 diam. 
Fig. 22. Septal plane of a specimen of Dendritina, showing the punctations contmued 
over its surface : — 100 diam. 
Fig. 23. Portion of the surface of a specimen of Penerojplis, on which the plications had 
become obsolete, but the punctations are still arranged m rows corresponding 
to them in distance : — 100 diam. 
Fig. 24. Portion of the surface of a specimen of Peneroplis, over which the punctations 
are scattered without definite arrangement : — 100 diam. 
PLATE III. 
Figs. 1-9. Side and front views of specimens of Oj^erculina at various ages, showing 
differences in the form and proportions of the spire, in the surface-markings, 
and in the number and arrangement of the tubercles marking the septal 
bands : — 10 diam. 
Fig. 10. Hemispherical cluster of tubercles occupying the umbilicus of the variety of 
O^erculina represented in figs. 11, 12 : — 25 diam. 
Figs. 11, 12. Side and front views of young and mature specimens of peculiar variety 
of O^erculina^ characterized by the rapid opening-out of the spire, and by the 
extraordinary development of tubercles, not only along, but also between the 
septal bands: — 10 diam. 
PLATE IV. 
Fig. 1. Part of the internal surface of one of the chambers of an Operculina ih.'di pre- 
sented large tubercles on its exterior, showing the uniform distribution of the 
tubuli except along the septal bands, and the comparatively large size of their 
orifices:™ 120 diam. 
Fig. 2. Section through the wall of a contiguous chamber of the same, showing the 
partial deficiency of tubuli in certain spots, with their crowding together in 
