MARINE DIATOMS OF THE PHILIPPINE ISLANDS 143 



Achnanihes, and generally somewhat twisted on its long axis, so that 

 in girdle view the frustule has an angular or bowed outline; and 

 second, the two valves being consequently dissimilar, their relative 

 convexity is different and the trend of the two rhaphes is also differ., 

 ent, one becoming more sigmoid than normal and the other less so. 



RHOICOSIGMA COMPACTUM (Greville) Grunow 



(Peragallo, Pleuro., pi. 10, figs. 7-8; Micro. Journ., 1857, pi. 3, fig. 9.) 



RHOICOSIGMA OCEANICUM Peragallo 



(Peragallo, Pleuro., pi. 10, figs. 5-6.) 



RHOICOSIGMA ROBUSTUM Grunow 



(Peragallo, Pleuro., pi. 10, figs. 2-3.) 



RHOICOSIGMA WEISSFLOGII Grunow 

 (Peragallo, Pleuro., pi. 9, figs. 23-24.) 



Genus ROPERIA Grunow 



ROPERIA TESSELATA (Roper) Grunow 



Plate 31, fig. 3 



(Van Heurck, Synopsis, pi. 118, figs. 6-7; Quart. Journ. Micro. Sci., 1858, pl v 

 3, figs, la-b.) 



Only one species of Roperia is known at present. But a variety so. 

 marked and constant as to almost deserve specific rank is a broadly 

 ovoid form in which the pseudonodule is invariably located in the 

 narrow end. The rim also is marked diagonally instead of transversely 

 so that the outer marginal line has a fictitious wavy appearance, 

 especially when slightly out of focus. This is the prevailing form in 

 Philippine Islands material. Its deviation from the type is so strik- 

 ing that it is here illustrated. 



Genus RUTILARIA Greville 



RUTILARIA PHILIPPINARUM Cleve and Grove 



(Le Diat., 1891, p. 64, pi. 10, figs. 1-2.) 



RUTILARIA PULCHRA A. Schmidt 



(Schmidt, Atlas, pi. 183, fig. 20.) 



Schmidt says of the locality merely "S. Monica." As Santa Monica, 

 Calif., is on the seacoast and a fossil diatom deposit is there, this state- 

 ment is ambiguous. Presumably his type specimen was from the 

 fossil material which is given special prominence in his atlas. I have 

 found it also in the fossil deposit at Jackson's Farm, Oamaru, New 

 Zealand. In that case, the finding it in the Philippine Islands is 

 especially interesting. 



