Mr. C. lyicresclikowsky on CaUforninn Ih'atonis. 293 



4. Diploneis geminata, var. typica, CI. Oiilif. guano. [(7.] 



5. Diploneis papula, A. S. Santa ]iIonica, amongst Macro- 



cyst is^ not rare ; Monterey, rare. [M.] 

 The endoclirome ot'tliis species (PI. IV. fig. 26) is very inter- 

 esting; it is composed of two plates, wliicli, liowever, 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. 



G. Diploneis splendida, var. puella, A. 8. [C] 



7. Diploneis subcincta, A. S. [C] 



8. Diploneis vacillans, A. S. [C] 



9. Diploneis vacillans, var. delicatula, CI. Santa Monica, 



recent. [M.] 



Length 0*043 nun., breadth of the valve 0'017 mn). 



10. Caloneis formosa, Greg. San Pedro, not rare. [C, M.] 



11. Caloneis formosa, var. quadrilineata, Grun. [C] 



12. Caloneis liber, var. elongata, Gnin, Rare. [M.] 



13. Caloneis Schumanniana, var. trinodis, Lewis. [C] 



14. Navicnla approximata, Grev. Calif, guano. [C] 



15. Navicula ( Schyzonema ) avenacea, Breb. San Pedro, 

 common. [M.] 



16. Navicula cancellata, Donk. San Pedro, not very common. 



Strife .0 in 001 mm. Chromatophores with margins pro- 

 foundly ."inuated. 



17. Navicula clavata, var. caribaea, CI. (forma minor). 



Northern California, not very rare. [M.] 



18. Navicula directa, var. heterostriata, Mer. (Mereschkowsky, 

 On Pulyii. Diat. part iv.). Nortliern California, rather 

 common. [M.] 



19. Navicula Febigerii, CI. [C] 



20. Navicula forcipata, Grev. San Pedro, rare. [C, M.] 



21. Navicula forcipata, var. densestriata, A. S. San Pedro, 



not rare. [M.] 

 Tlie form which I have observed has the fine striation 

 cliaracteristic of this variety, but the lateral areas are not or 

 scantily constricted in tbe 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 



