506 Mr. C. Mereschkowsky on Californian Diatoms. 
middle, with rounded ends; length 0°04-0:'140 mm., breadth 
0:022-0:028 mm. Structure composed of coste, which, 
however, are very indistinct, almost invisible with an ordinary 
magnifying-power, the intercostal alveoli forming parallel 
strie becoming radiate near the ends, which are smooth. 
Pseudoraphe very narrow, sometimes indistinct. Number of 
strie 5°5-6°5 in O'OL mm. Number of puncta 8 in 0°OL mm. 
Girdle-face as in 2. arcuatum, but with finer transverse coste, 
usually 8 (from 6 to 10) in 0-OL mm. 
Fig. 21 shows a valve as it appears under an ordinary 
magnifying-power, the costa not being seen and the rows of 
puncta resembling those of Achnanthidium brevipes; fig. 22 
is a part of the valve under a greater magnifying-power. 
This species, which has probably already been described *, 
but which for lack of necessary books I am unable to deter- 
mine, is very frequent in the Aleutian Islands, and I possess 
it also in a slide labelled “ California,” without further indi- 
cation of locality. Other species which this slide contains 
indicate that it comes from Northern California. 
137. Entopyla incurvata (Arn.), Grun. Not rare in Southern 
Calitornia (Catalina ; Clemente Islands and the coast, 
Haliotus washings) ; Californian guano. [M.] 
Length 0°121-0-217 mm. ; girdle-face of a large specimen 
0-01 mm.; distance between two coste 0°007 mm. 
138. Gephyria media, Arn. Jtedondo Beach, not rare ; Mon- 
terey, rare. [M.] 
Length 0:196 mm., breadth of the girdle-face attaining 
0057 mm.; strie 5 in 0'OL mm. Endochrome granular, 
composed of 30-40 large granules. 
139. Grammatophora angulosa, Ehr. San Pedro, very rare. 
[M.] 
140. Grammatophora angulosa, var. hamulifera, Kiitz. San 
Pedro, Monterey, very rare. [M.] 
141. Grammatophora arctica, Cl. Not rare in Monterey and 
in Northern California, rare in Southern (/laliotus 
washings). [M.] 
Valve linear, very slightly attenuated towards the apices, 
breadth 0-007 mm.; striz distinct, 12 in 0-01 mm., com- 
posed of distinct puncta; length of the frastule O-028- 
0-054 mm., breadth 0°01d-0°021 mm. ; septa forming two or 
* If not, its proper name would be R&. gibboswn. 
