Mr. C. Mereschkowsky on Californian Diatoms. 293 
4, Diploneis gemmata, var. typica, Cl. Calif. guano. [C.] 
5. Diploneis papula, A.S. Santa Monica, amongst JMJacro- 
eyst’s, not rare; Monterey, rare. [M.]| 
The endochrome of this species (PI. IV. fig. 26) is very inter- 
esting ; it is composed of two plates, which, however, are not 
disposed only along both sides of the valve, leaving its apices 
free, as is usually the case in the Naviculoid Diatoms, but 
partly enter into the other half of the valve, thus occupying 
both ends of the frustule. 
6. Diploneis splendida, var. puella, A. 8. [C.] 
7. Diploneis subcincta, A. 8. [C.] 
8. Diploneis vacillans, A. 8S. [C.] 
9. Diploueis vacillans, var. delicatula, Cl. Santa Monica, 
necent., || M1. 
Length 0°043 mm., breadth of the valve 0°017 mm. 
10. Caloneis formosa, Greg. San Pedro, not rare. [C., M.] 
11. Caloneis formosa, var. quadrilineata, Grun. [C. | 
12. Caloneis liber, var. elongata, Grun. Rare. [M.] 
13. Caloneis Schumanniana, var. trinodis, Lewis. [C. | 
14, Navicula approximata, Grev. Calif. guano. [C.] 
15. Navicula (Schyzonema) avenacea, Bréb. San Pedro, 
common. [M.] 
16, Navicula cancellata, Donk. San Pedro, not very common. 
[ M.] 
Strie din 0-01 mm. Chromatophores with margins pro- 
foundly sinuated. 
17. Navicula clavata, var. caribea, Cl. (forma minor), 
Northern California, not very rare. [M.] 
18, Navicula directa, var. heterostriata, Mer. (Mereschkowsky, 
On Polyn. Diat. part iv.). Northern California, rather 
common. [M.] 
19. Navicula Febigerii, Cl. [C.] 
20. Navicula forcipata, Grev. San Pedro, rare. [C., M.] 
21. Navicula forcipata, var. densestriata, A. S. San Pedro, 
not rare. [M.] 
The form which I have observed has the fine striation 
characteristic of this variety, but the lateral areas are not or 
scantily constricted in the middle. I have succeeded in 
examining a frustule in a vertical position and obtaining in 
this way an optical section through it, which is represented 
