38 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



beneath the network consist of closely set beading in strictly radial 

 arrangement; a single small but evident spine in the center of each 

 hexagon. The name refers to the laterally parallel rows of the net- 

 work contrasted with the radially arranged rows of the beading. 



Diameter (from apex to middle of opposite side) 0.25 mm. ; diameter 

 of hexagons (average), 0.007 mm.; rows of beading (average), 13 in 

 0.01 mm. 



This B. favus-like diatom has some resemblance to two other forms, 

 B. ( Triceratium) broeckii Leuduger-Fortmorel (Schmidt, Atlas, pi. 82, 

 figs. 10, 12) and B. {Triceratium) scitulum Brightwell (Micro. Journ., 

 1854, pi. 4, fig. 9). 



Type.— Cat. No. 43591, U.S.N.M. 



BIDDULPHIA DISTINCTA (Janisch) Mann 



(Schmidt, Atlas, pi. 83, fig. 1.) 



BIDDULPHIA DUBIA (Brightwell) Cleve 



(Micro. Journ., 1859, pi. 9, fig. 12; Schmidt, Atlas, pi. 78, figs. 32-35.) 



I include with this Cleve's Triceratium bicorne (Schmidt, Atlas, pi. 

 78, figs. 24-25). The species has alsO close affinities with Biddulphia 

 reticulata Roper, which almost justify their union. 



BIDDULPHIA EXACTA, new species 



Plate 9, fig. 1 



Valve triangular, side slightly convex, apices not produced ; proc- 

 esses nearly sessil, tilted outward; the entire surface covered with a 

 large, strong-walled, hexagonal network arranged in exactly straight 

 lines perpendicular to the three sides, the areolation only slightly 

 smaller toward the margin; beneath the areolation are secondary 

 markings of extremely minute beads, obscurely, if at all, radial in 

 arrangement; a sharp slightly curved spine in the center of each 

 hexagon; in side (or girdle) view the top of the valve is seen to be 

 flat and closely set with the above-mentioned spines, the three horns 

 protruding at an angle of 45° and the sides below these being recessed; 

 the rim (adjacent to the girdle) extends beyond the tips of the horns: 

 the girdle is broad and entirely covered with close beading, arranged 

 in quincunx order. 



This side view of the entire frustule is accurately figured in 

 Schmidt, Atlas, plate 87, figure 6, and it is a proof of the keen obser- 

 vation of that author that he suspects this evidently solitary specimen 

 brought to his attention to be a new species, but refrains from nam- 

 ing it. His specimen is marked as coming from the near-by North 

 Celibes. In the Philippine Islands it seems also to be rare. 



Diameter (apex to middle of opposite side) 0.144 mm.; height of 

 frustule 0.107 mm. 



Type.— Cat. No. 43592, U.S.N.M. 



