MARINE DIATOMS OF THE PHILIPPINE ISLANDS 67 



figure in Schmidt's Atlas, plate 65, figure 11. Only one, but an 

 unmistakable specimen, of this diatom was found, the type of which 

 is marked as coming from "Piscataway." 



COSCINODISCUS JANISCHII A. Schmidt 



(Schmidt, Atlas, pi. 64, figs. 3-4.) 



COSCINODISCUS KUETZINGII A. Schmidt 



(Schmidt, Atlas, pi. 57, figs. 17-18; Gran, Nord. Plank., p. 36, fig. 38.) 



COSCINODISCUS LENTIGINOSUS Janisch 



(Janisch, Gaz. Exp., pi. 5, fig. 7.; Schmidt, Atlas, pi. 58, fig. 11.) 



COSCINODISCUS LEPTOPUS Grunow 



(Van Heurck, Synopsis, pi. 131, figs. 5-6.) 



This is easily confused with C. lineatus Ehrenberg, which see. 



COSCINODISCUS LINEATUS Ehrenberg 



(Ehrenberg, Mikrogeologie, pi. 18, fig. 33; pi. 22, fig. 6a, b; Van Heurck, 

 Synopsis, pi. 131, fig. 3; Schmidt, Atlas, pi. 59, figs. 27, 32.) 



If there were need to select the the six most important diatoms 

 this would be one. Its present geographical distribution is almost 

 universal; and its general presence in fossil deposits from all parts 

 of the world indicates it is one of a few species that have held their 

 type characteristics unchanged from the beginning. Whether or not 

 certain forms similar to it have branched off from it as the parent 

 stock, it is at present impossible to say. But the resemblance of 

 C. excentricus and C. leptopus to it is worthy of comment, when taken 

 in connection 'with the fact that one does find occasionally individuals 

 in which the linear network is disturbed so as to duplicate that 

 of C. excentricus, and also there occur cases in which the single rod- 

 like process on the margin of C. leptopus can be discovered on the 

 margin of this species. The above figures in Van Heurck and in 

 Schmidt's Atlas will enable one to distinguish between these similar 

 forms. 



COSCINODISCUS MARGINATUS Ehrenberg 



(Ehrenberg, Mikrogeologie, pi. 18, fig. 44; pi. 33, sec. 12, fig. 13; Schmidt, 

 Atlas, pi. 62, figs. 1-5.) 



For a discussion of the haphazard use of this name and Coscino 

 discus robustus Greville, see Mann 's Diatoms of the Albatross Voyages, 

 page 254. There are also some figures bearing this name which clearly 

 belong to other species; for example, the one in Schmidt's Nord- 

 seefahrt Diatomaceen, plate 3, figure 35, which is C. Tcutzingii A. 

 Schmidt. 



As bearing on this subject it may be here stated, that a recent exami- 

 nation of many specimens of Coscinodiscus robustus Greville, collected 



