120 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



spacing and size of beads than on the opposite side, and the last 

 bead in each row, adjacent to the rhaphe, is enlarged, which is not 

 the case on the opposite side; the central nodule is conspicuous and 

 is unsymmetrically placed nearer to this side, the middle termina- 

 tions of the rhaphe also being bent toward this side. 



Length, 0.141-0.211; width, 0.034-0.045; 8 lines in 0.01 mm. 



One is reminded by this species of N. (Alloioneis ?) Icurzii Grunow 

 (Cleve, W. I. Diat., p. 8, pi. 2, fig. 12). It is not infrequent in sev- 

 eral of the Philippine Islands dredgings. 



Type.— Cat. No. 43661, U.S.N.M. 



NAVICULA SEPARABILIS A. Schmidt 



(Schmidt, Atlas, pi. 11, figs. 3-5, 7, 10.) 



This is another species common to both Campeche Bay and the 

 Philippine Islands. The claim implied in its specific name is prob- 

 ably justified, although it is rather close to N. crabro Ehrenberg. 



NAVICULA SERRATULA Grunow 



Plate 26, fig. 6 



(Schmidt, Atlas, pi. 7, figs. 42-43.) 



This is another species peculiar to Campeche Bay and the Philip- 

 pine Islands, unless the unnamed figure of a Samoa diatom in 

 Schmidt's Atlas, plate 8, figure 11, is this species. Fricke's Index 

 considers it the same, probably correctly so. The Philippine Islands 

 form is here illustrated. 



NAVICULA SIMULATOR, new species 



Plate 26, fig. 7 



Valve nearly flat, very broadly elliptical, with straight sides and 

 rounded ends, densely covered, except in the narrowly elliptical 

 median area that is bisected by the rhaphe, with fine but strongly 

 beaded, closely set lines, a single row of beads to each line, trans- 

 verse at the middle part of the valve, increasingly diagonal and 

 curved toward each end, until at the extreme ends they become truly 

 longitudinal; the middle area of the valve is narrow, barely elliptical 

 not widened at its center and not tapering; its ends set some distance 

 back from the rounded ends of the valve; the rhaphe bisecting this 

 middle area is heavy, its apical ends forked and turned toward the 

 same side of the valve; the central nodule is slighty dilated; the 

 middle area is, on either side of the rhaphe, marked with very 

 obscurely beaded continuations of the beaded lines covering the 

 outer portions of the valve. 



Length, 0.095; width, 0.051; 9 lines in 0.01 mm. 



This elegantly sculptured diatom has its nearest affinity in N. 

 aestiva Donkin, which, however, has less clearly cut beading than N. 



