152 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



SURIRELLA COMIS A. Schmidt 



(Schmidt, Atlas, pi. 4, figs, 3-7; pi. 20, fig. 3.) 



SURIRELLA CONCENTRICA, new species 



Plate 34, fig. 1 



Valve broadly oval, its outer band or rim narrow but stoi**,, cross- 

 barred with closely set lines and bisected by a fine wavy median line, 

 the outer half of the rim being further ornamented with widely sep- 

 arated, evenly spaced, shadowy rings or dots; within the rim narrow 

 ribs or costae proceed radially toward the center, making a band 

 about one-quarter the width of the valve in diameter and leaving a 

 hyaline central area about one-half the valve's diameter in size, in 

 which there is no median line ; each costa begins at the outer band 

 with a hardly perceptible enlargement, but is bordered for a short 

 distance near its middle part with a row of fine beads on either side; 

 these double rows of beads taken together appear as a smaller con- 

 centric band passing across the middle of the costal bands; polar 

 areas terminating the longer axis are well defined, and are each 

 marked with a semicircular protuberance. 



Long diameter, 0.157; short diameter, 0.114 mm. 



Type.— Cat. No. 43682, U.S.N. M. 



SURIRELLA CONTIGUA, new species 



Plate 34, fig. 2 



Valve elongated ovate, one end much broader than the other; outer 

 rim a narrow band; no alae; the costae begin at the outside margin, 

 crossing the rim and approaching almost to the center of the valve, 

 but leaving a pronounced tortuous hyaline central area, extending 

 the length of the valve ; the costae in the middle portion of the valve 

 are transverse, but near each end become rapidly more radial and 

 outwardly curved ; between the costae are fine, closely set parallel 

 fines of minute beading, three to six between each pair of costae. 



Long diameter 0.073-0.126; short diameter 0.038-0.071; 17.5 fine 

 lines in 0.01 mm. 



This species bears an interestingly close resemblance to the fresh- 

 water diatom S. gemma Ehrenberg, the similarity being referred to in 

 the specific name here selected. Its intercostal lines are somewhat 

 coarser and its strongly ovate shape and broad central area sharply 

 differentiate them. A very similar but much larger species occurs 

 at Panama and is here figured for comparison; see plate 34, figure 3. 

 I have named it S. foliata, new species. It will be described in a 

 forthcoming paper on the Diatoms of Panama. 



Type.— Cat. No. 43683, U.S.N.M. 



