MARINE DIATOMS OF THE PHILIPPINE ISLANDS 147 



Genus STICTODESMIS Greville 



STICTODESMIS AUSTRALIS Greville 



(Greville, Diat., So. Pac, p. 34, pi. 1, figs. 1-4; Van Heurck, Treat., p. 237, fig. 

 34.) 



The validity of both the generic and specific names of this diatom 

 deserves discussion. First, as to this being a valid genus: It is 

 claimed by several diatomists that the species of this genus are noth- 

 ing more than certain diatoms belonging to other genera but which 

 develop craticular plates ("dissepiments") within the frustule, one 

 beneath each valve, similar to the craticular plates of such diatoms 

 as Navicula cuspidada Kiitzing, the separated plates of which long 

 went under the name of Surirella craticula Ehrenberg. Thus the 

 present species, S. australis, is said to be the craticular state of Navic- 

 ula scopulorum Brebisson ( = Pinnularia johnsonii W. Smith) accord- 

 ing to Van Heurck, Treatise, page 237, Peragallo's Diatomees de la 

 France, plate 8, figure 28, Cleve's Naviculoid Diatoms, volume 1, 

 page 152, etc. S. australis is quite abundant at Jolo Jolo, Sulu 

 Islands, Philippine Islands, and has afforded material for a study of 

 the complete frustules and of the valves and their internal dissepi- 

 ments mounted separately. Navicula scopulorum is also abundantly 

 supplied for comparison in H. L. Smith's Types, No. 286. The valves 

 of the two are so similar as to make the claim of their being identi- 

 cal a strong one. But even the valves themselves show certain note- 

 worthy differences, those of S. australis being much narrower and 

 very often curved sideways, so as to take on a sickle shape. The 

 rhaphe too is more delicate and with terminations at the center and 

 apices of the valve that remind one of the rhaphe of Frustulia rhom- 

 boides (Ehrenberg) De Toni. But the important point is that the 

 internal dissepiments are wholly unlike the occasional craticular plates 

 found in other diatoms. They are not irregularly constructed plates, 

 the ribs of which sometimes run transversely from side to side below 

 the valves and sometimes anastomose into an irregular network; 

 but they are the exact counterpart of the dissepiments of Climacosphe 

 nia, having cross ribs formed into a regular ladder, the opening 

 between these rungs at the middle of the valve being always double 

 that of the others; and at the center of each rung, as in Climacosphe- 

 nia, is a knot where the two halves join. It is quite certain that if 

 Strictodesmis is invalid, so also is Climacosphe nia; if the former is a 

 dimorphic phase of Navicula, Climacosphenia, is a dimorphic phase 

 of Licmophora. Grunow's useful genus Campyloneis separates such 

 forms as C. grevillei from the genus Cocconeis because of just such 

 internal dissepiments as those here discussed, being identical with 

 them in structure and position. So that if the present genus falls to 

 the ground, Campyloneis must fall with it. Nor can Mastogloia be 

 kept separate from Navicula by any definition that will not also jus- 



