124 
GrevillE; on New Diatoms. 
lines of very minute puncta^ closely radiating from the very 
centre, and terminating towards the margin in a belt of still 
smaller irregularly crowded punct a; processes small, 6; margin 
striated. Diameter -0030'^ (Fig. 4.) 
Hab, Moron deposit, Province of Seville; Rev. T. G. 
Stokes. 
This species differs from C. pulchelluSy with which it agrees 
in form and size, in the crowded character of the radiating 
lines which fill the disc, and in the very much smaller 
number of processes. The latter are somewhat inconspicuous. 
The puncta which form the band between the radiating lines 
and the striated margin are smaller than the others, and 
irregularly crowded. I am obliged to my indefatigable 
friend Mr. Stokes for having brought this addition to the 
genus under my notice. 
RuTiLA-RiA (char, amended). 
Frustules very compressed, cohering into a short filament ; 
valves slightly elevated at the angles, with a central glistening 
nodule prolonged into two short, linear, obtuse processes ; the 
margin pectinate-ciliate. 
The fortunate discovery of perfect frustules in situ enables 
me to determine the true position of this very interesting and 
curious genus, three species of which were published in the 
'Quart. Journ. of Mic. Sci.,' Vol. Ill, New Series. At 
that time nothing more was known of them than what was 
afforded by a side view of the valve, which, however, was 
sufficient of itself to separate them from all known diatoms. 
The genus is unquestionably allied, as my friend Mr. T. G. 
Rylands suggests, to the Biddulphiea. The angles of the 
valves are not prolonged into horns, but are only slightly 
elevated, and consequently the valves of opposite frustules, as 
seen in the front view, are brought so near together that the 
marginal cilise^ of each nearly cross the intervening space. 
The best view of the structure, showing its affinity with the 
Biddulphiece, is to be obtained from the valve when so placed 
as to present both the front and lateral surfaces. (Fig. 10.) 
The genus, in fact, passes into Biddulphia through B. fim- 
briata, and especially through B. spinosa. Mr. Rylands, who 
with his usual kindness and acuteness examined, at my 
request, R. elliptica very critically, satisfied himself that of 
the two central processes one was straight and the other 
curved, as in the flexure of the forefinger ; and that the pro- 
cesses of the opposing valves were interlocked, the straight 
process of the one passing mutually through the curved pro- 
