156 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



six spines on the outer edge, the two side spines being largest; the 

 costae running inward from these plates are narrow but deep and 

 therefore sharply defined, radial, each with a slight angular bend at 

 its middle; no central area; polar areas large. 



Diameter, 0.061 mm. 



There are a number of circular Surirellae, simulating the genus 

 Camjjylodiscus, but without the double bend of that genus; none 

 resemble the present species closely. 



Type.— Cat. No. 43688, U.S.N.M. 



SURIRELLA INCURVATA A. Schmidt 



See S. deflexa A. Schmidt. 



SURIRELLA INTERCEDENS Grunow 



(Schmidt, Atlas, pi. 19, figs. 5-6.) 



SURIRELLA LATA W. Smith 



(Smith, Brit. Diat., pi. 9, fig. 61; Schmidt, Atlas, pi. 5, fig. 1; Schmidt Nordsee, 

 pi. 3, fig. 9.) 



De Toni's union of this with S. fastuosa is not warranted. The 

 ribs of the latter are longitudinally striped; of the former marked 

 with a cluster of closely set beads at the inner end of each rib, which 

 is very short and broad. 



SURIRELLA LAXA Janisch 



(Janisch, Gaz. Exp., pi. 21, figs. 25-27; Schmidt, Atlas, pi. 56, figs. 3-4.) 



The finely beaded margins of the short, heavy ribs is finely brought 

 out in Schmidt's figures. 



SURIRELLA MACRAEANA Greville 



Plate 34, figs. 5-7; plate 35, fig. 1 



(Micro. Journ., 1862, pi. 2, fig. 1; Janisch, Gaz. Exp., pi. 16, figs. 2-4; pi. 19, 

 fig. 1.) 



The great variability of this species has induced me to give four 

 figures, that of the girdle view being specially needed in diatom 

 literature. 



SURIRELLA MOLLIS A. Schmidt 



See S. schleinitzii. 



SURIRELLA ORIENTALIS, new species 



Plate 36, fig. 1 



Valve elliptical, slightly constricted at the middle; that is, imper- 

 fectly panduriform; rim broad, heavy, coarsely crossbarred; alae 

 obscure or wanting; costae beginning with lozenge-shaped pointed 

 plates elevated above the rim, thence extending transversely to the 

 middle, except at the ends of the valve, where they become oblique; 



