Mr. C, Mereschkowsky on Californian Diatoms. 515 
varies greatly. If the lesser coarseness should prove to be a 
constant character, then, of course, a separate variety—var. 
tessellata—could be established, as the true B. antediluviana 
of Europe has invariably very coarse alveoli; but having 
seen only one individual of that kind, I regard this case as an 
accidental one. Therefore the best would be, in my opinion, 
to unite B, tessellata and B. antediluviana in one species. 
196. Biddulphia (Triceratium) arctica, Brightw. Northern 
California; Monterey, not rare. [G., M.] 
197. Biddulphia (Triceratium) arctica, var. tetragona, Grun. 
Northern California, common ; Monterey, rather rare. 
(G] 
198. Biddulphia (Triceratium) montereyi, Brightw.* San 
Pedro, rare; Northern California. [G., M.] 
199. Biddulphia (Triceratium) sanpedroana, Mer., sp. n. 
(BIA «ig. 27.) ‘San-Pedro, not rare. -_[.M.] 
Differs from B. (Amphitetras) punctata, Grev.t, which is 
found in Ceylon, by the puncta or alveoli being more rounded 
and not so closely disposed, the margins of the valve not so 
deeply concave, and the processes less elongated, broader, and 
more rounded. There seems to be a difference also in the 
central part of the valve, which in B. punctata shows a well- 
defined central area with a few scattered granules. 
‘The puncta are sometimes a little larger than represented 
in my figure, sometimes they are smaller and more distant, 
but the valve has always about the same shape, its processes 
never being so prominent and acute as in the type species. 
The central part of the valve is concave and the concavity 
has sometimes a quadrangular form with angles opposite to 
the middle part of the concave margins ; if in such individuals 
the puncta are at the same time very small, they greatly 
resemble B, elegans, Grev. B. (Triceratium) sanpedroana is 
no doubt nearly allied to B. (Triceratium) antediluviana. 
Number of puncta usually 3°5 in 0-01 mm. (from 8 to 4), 
greatest diameter (along a diagonal) 0-063-0'119 mm., smallest 
diameter 0°049-0:091 mm. 
This diatom is widely distributed all over the Pacific Ocean. 
I have found it also in the fossil deposit of Redondo (Cali- 
fornia). 
200. Biddulphia (Triceratium) uncinnata, Grun. (See Wolle, 
Diat. Amer. pl. cil. fig. 12.) 
* Loe, cit. pl. i. fig. 18. Tt Loe. cit. pl. xiii, fiz. 8. 
