MABINE DIATOMS OF THE PHILIPPINE ISLANDS 57 



CHAETOCEROS (BACTERIASTRUM) MEDUSA, new name 



Plate 12, figs. 1, 2 

 (Castracane, Chall. Exp., pi. 28, fig. 6, misnamed.) 



This above-misnamed diatom is not a variety of B. wallichii Ralfs. 

 (See Pritchard, Inf., p. 863, pi. 6, fig. 27.) Nor can it possibly be 

 the same as what Castracane also calls C. wallichii in the Report of 

 the Challenger Expedition, plate 23, figure 3. Ralfs' form is the 

 Chaetoceros bacteriastrum, Wallich (Micro. Journ., 1860, pi. 2, figs. 

 16-17). The specimen in the Report of the Challenger Expedition 

 (pi. 29, fig. 6) came from Hongkong. See same from Gulf of Siam 

 (Schmidt, Atlas, pi. 328, fig. 12, misnamed.) 



Diameter of disk, 0.031; diameter including arms to their right- 

 angle bend, 0.107; length of rest of arms from bend to tip, 0.072; 

 length of entire arm therefore, 0.21 mm. 



CHAETOCEROS (BACTERIASTRUM) PRINCEPS, new name 



Plate 12, fig. 3 



This is the form figured in the Report of the Challenger Expedi- 

 tion, plate 29, figure 3, and incorrectly named B. varians Lauder, var. 

 princeps Castracane. It is wholly different from Lauder's form 

 which, contrary to what Castracane says, has its arms spirally wound 

 with a prickly line, sometimes two. The large circular valve of this 

 species ; the deep socketing of the arms or rays>; the large number of 

 these, 25; and the very convex valve, hyaline except for a central 

 bead or umbo, combine to make it sufficiently dissimilar from B. varians 

 to warrant a new name. I question its being the terminal form de- 

 scribed in the Report of the Challenger Expedition (pi. 14, fig. 2), 

 which is probably B. hyalinum Lauder. (See Micro. Journ., 1864, pi. 

 3, fig. 7a.) But it should be added that, as no good figure or descrip- 

 tion of the terminal valve of B. hyalinum Lauder is known, I can not 

 affirm that my own form will not prove to belong to that species. 

 As pointed out elsewhere, the specific name "varians" has doubtless 

 been responsible for referring almost every Bacteriastrum-sheLped 

 Chaetoceros to this convenient depository. 



Diameter of disk, 0.047; diameter with arms, 0.189 mm. 



CHAETOCEROS SCOLOPENDRA Cleve 



(Gran, Norweg. N. Atl. Exp., pi. 4, fig. 53; Cleve, Plankt. Sweden, pi. 1, fig. 5.) 



This sharply marked species is quite common at the Philippine 

 Islands. 



CHAETOCEROS SOCIALE Lauder 



(Micro. Journ., 1864, p. 77, pi. 8, fig. 1; Gran, Nord. Plank., fig. 123.) 



Doubtless this diatom is more abundant than is recorded. It is 

 easily overlooked in water or Canada balsam mounts, but shows up 

 well in high refractive media, like barium-mercuric iodide. 



