STILL FOUND IN A LIVING STATE. 339 
are merely supernumerary collateral filaments, cirrhi, together 
with a minute foot, such as the other Navicule have. Longi- 
tudinal fissures and central apertures on the broad side of the 
shell are not present; but more than six, and to the number of 
ninety-six, lateral apertures for the cirrhi are discernible. Per- 
haps this form may constitute the type of a distinct group of the 
Bacillarie. I have besides recently convinced myself that the 
Navicule in general differ considerably in structure, as I have re- 
cognised distinctly the six round shell-apertures in many species 
also, as well as in Nav. viridis; but in some gaping fissures near 
them, and in others as yet undescribed gaping fissures without 
round apertures. These possibly generic or subgeneric distinc- 
tions may explain differences of opinion of various observers, 
who, from different objects, may have inferred a diversity of re- 
lations. The above species I have named, from its transparent 
large shield, Nav. Gemma. 
VI. Further communications on recent Organisms of the Chalk*, 
October 31st, 1839. 
Part of the animals of the chalk marl are still living in Berlin, 
_ in the sea-water collected on the 22nd September at Cuxhaven ; 
and by continued examination I have even discovered additional 
species. Of especial interest are two new large species of the 
genus Actinocyclus, one with 8 chambers and 16 rays (septa), 
the other with 9 chambers and 18 rays, which have been desig- 
nated as Actinocyclus sedenarius, and octodenarius. 
But besides this, a new phenomenon has occurred which 
awakens a still more general geological interest ; for, besides the 
above-mentioned living siliceous-shelled Infusoria, two species 
of still living microscopic Polythalamie have also been found 
which bear decidedly the character of two of the most exten- 
sively diffused calcareous-shelled animalcules of the chalk,— 
namely, Planulina (Rotalia?) turyida, and Tevxtilaria aciculata. 
Both forms were recognised in a few specimens, and afterwards 
in several, but unfortunately not early enough to submit to ex- 
amination fresh and lively animalcules. In Planulina change of 
place has been observed, but the organs of locomotion remained 
_ * This and the following additions I have considered advantageous to insert 
here, with the permission of the Academy, in order to render complete the 
scientific view of our entire knowledge of the subject up to the printing of the 
memoir. ‘These observations were communicated on the 3l1st of Oct. 1839; 
those of the following section on the 16th of Jan. 1840, under which date they 
will be found noticed in the Reports of the Academy. 
