MARINE DIATOMS OF THE PHILIPPINE ISLANDS 61 



COCCONEIS CIRCUMCINCTA A. Schmidt 



See under C. pellucida Grunow. 



COCCONEIS CITRINA A. Schmidt 



(Schmidt, Atlas, pi. 198, figs. 28-30.) 

 See remarks under next species. 



COCCONEIS CITRONELLA, new species? 



Plate 13, figs. 3-6 



Valves broadly oval with apiculate apices; lower valve with deli- 

 cate radiating beaded lines closely set, slightly more evident in a 

 band near each margin, otherwise very obscure and misty; almost 

 reaching the rhaphe but lacking on either side of the central nodule, 

 so that a hyaline stauros is produced which is about one-fifth the 

 width of the valve; upper valve with widely set rows of coarse rec- 

 tangular beads radially arranged and slightly curved toward the two 

 apices, the outer beads of these rows next to the margins of the valve 

 being plainly larger than the others; a hyaline median line corre- 

 sponding to the rhaphe line of the lower valve. 



Length of valve 0.062-0.070; width of valve 0.034-0.039; lines on 

 upper valve 6.5 in 0.01 mm.; lines on lower valve 21-25 in 0.01 mm. 



Great confusion exists about this and some similar species, as the 

 result of Cleve's arbtirary grouping of several dissimilar forms under 

 Achnathes mammalis (Castracane) Cleve in his Naviculoid Diatoms, 

 volume 2, page 187, plate 3, figures 13-16. His name is based on 

 RJiaplwneis mammalis Castracane (Chall. Exp., p. 48, pi. 26, fig. 3) 

 which, although not a EliapJioneis , is equally not an Achnanthes. 

 But more important is it that both from the figure and the ample 

 description of Castracane, it is evident that we have there a valve 

 with coarse unbeaded costae, in no respect like Cleve's diatom except 

 in the similarity of outline. Cleve's form seems to be the same as 

 the diatoms figured in Schmidt's Atlas, plate 198, figures 35, 36, 40, 

 all from Yokohama and all left unnamed by Schmidt. It might be 

 possible to consider these as varieties of Cocconeis citrina A. Schmidt, 

 as figured in his Atlas, plate 198, figures 28-30, except that the lower 

 valve of the species as shown in figure 30 is very different. The 

 beading also is less rectangular and more widely spaced, and there is 

 not a trace of the minute double lines of beading shown in Cleve's 

 figure 14. It is also significant that Schmidt himself does not include 

 them in his C. citrina. It may be added that C. citrina also occurs 

 in the Philippine Island^ and is included in this report. There also 

 is no good reason for Cleve including with these Stauroneis apicidata 

 Greville (figured in Greville's Diat. Cal. Guano, pi. 4, fig. 8), a species 

 which Schmidt more reasonably makes Cocconeis apiculata (Greville) 



