TRANSACTIONS. 
Descriptions of New and Rare Diatoms. Series IV. 
By R. K. Greville, LL.D., F.R.S.E., &c. 
(Read June 12th, 1861.) 
Stictodiscus. 
Stictodiscus Californicus, n. sp., Grev. — Puncta equal, large, 
in rows of a single series ; rays obscure, terminating in 
conspicuous, linear-oblong bases witbin tbe broad margin ; 
central puncta somewhat remotely scattered. Diameter 
•0038'. (PL X, fig. 1.) 
Hab. Monterey stone. 
A genuine Stictodiscus, distinguished from S. Johnsonianus 
(which it resembles in the puncta, being arranged in single 
rows) by the obscure and much shorter rays, by the broad 
margin, and linear-oblong bases of the rays. Although the 
latter are decidedly obscure compared with the same parts in 
the other species, a careful adjustment shows their presence, 
as well as the anastomosing lines towards the centre, which 
exist in /S. Buryanus and S. Johnsonianus. When the sur- 
face of the disc is exactly in focus, the puncta appear simple ; 
but by slightly lowering the focus a pore becomes visible in 
the middle of each punctum ; and on viewing the valve from 
within, the pores are very conspicuous, and placed on the 
summits of little circular convex cavities (plane on the outer 
surface, convex on the inner surface, of the valve), strongly 
resembling the discs in the woody fibre of the Coniferse, 
which are themselves little, plano-convex boxes, with an 
orifice. The border of the disc is bounded by a row of 
minute puncta. The number of rays is upwards of forty. 
Stictodiscus Kittonianus, n. sp., Grev. — Disc umbonate, 
with a central nucleus ; rays numerous ; puncta minute, 
equal, forming a double series in each compartment, and 
closelv covering the central space. Diameter about '0020". 
(Figs: 2, 3.) 
VOL. IX. g 
