Mr. C. Mereschkowsky on Californian Diatoms. 479 
all these forms which have been confounded under the name 
of N. closterium * :— 
I. Girdle-face not differing from the valve- 
face, 
A. Length over 0-06 mm. 
a. Frustule arcuate. 
aa. Both or one end curved back- 
wards ; very large forms, attain- 
TNO OSMN IAs, «5c cos cinre sie sae et N. tenuirostris, var. arcus. 
bb. Ends not curved backwards. 
Frustule gently arcuate........ NV, tenuirostris (typica). 
Frustule soe arcuate, semi- 
circular. bee ates shee si NV. tenurrostris, forma 
b. Frustule straight, [semicircularis, 
Ends forming’a hook. os... 604 NV, tenuirostris, var. 
(hamulifera, 
Not forming a hook ........ .... LV. tenuirostris, forma 
B. Length 0:06 mm. or less. [ directa. 
Length about 0-05 mm. ...........- N, tenwrostris, var. parva. 
Length about 0-035 mm. ........ .. Nt. var. parva, forma 
Il. Girdle-face differing from the valve- “face. [minutissima, 
Rostra curved on the same side ...... N, gracilis. 
Rostra curved in contrary directions .. NV. gracilis, var. reversa. 
126. Nitzschiella californica, sp. n. (PI. IV. figs. 18-20.) 
Redondo Beach, common. [M.] 
Valve fusiform, abruptly terminating in straight rostra 
(fig. 18). Girdle-face (figs. 19, 20) asymmetrical, with one 
side straight and the other convex; rostra forming a knee- 
like curve at their junction with the body, thus being carried 
to one side. Hndochrome composed of two plates. General 
length 0-056—0-063 mm., length of the body 0°023-0-029 mm., 
breadth 0°0085-0°0055 mm. 
127. Cylindrotheca gracilis (Bréb.), Grun, (PI. IV. fig. 21.) 
San Pedro, rather common. [M.] 
I first observed this freshwater diatom in the Mediter- 
ranean (Villefranche) in purely mariue water, and now I have 
met with it again in San Pedro, in marine : ater too and i 
great abundance. The size is extremely variable, from 0°035— 
0:224 mm., breadth from 0°015-0:008 mm. The frustule is 
sometimes arcuate, especially in small individuals. The 
endochrome is composed of 2 to 36 rounded or elliptic granules 
arranged in a spiral along the umer walls of the frustule, 
128. Cymatopleura angulata, Grev. Calif. guano. [Gv.] 
* Small individuals of NM. diplacata have heen probably also confounded 
under this name. 
