SOME NEW AND RAKK DIATOMS. 



Triceratium Febi^eri, N. Sp., W. C. Walker. Valve triangular ; distance between 

 angles .006 inch; margins straight, interrupted midway by a convexity; angles rounded: 

 surface of valve coarsely granular: granules small and irregular at centre and angles, but larger 



and arranged in rows on remainder of surface. Habitat. Barbadoes ; VY. C. Walker. Plate 2, 

 Fig. 6. 



This is one of the most curious and interesting species yet given up by that apparently exhaust- 

 less wonder land, the Barbadoes fossil deposits. The peculiar appearance can be better under- 

 stood from a study of the illustration in our plate, which is a faithful representation of it. 



Podosira Pacifica, N. Sp.. II. IT. Chase. Large, measuring .0039 inch in diameter ; 

 finely striated over entire surface, striae radiant from center: margin wide and coarsely striated: 

 middle third of valve with from 18 to 30 large, circular openings, giving a coarse, seive-like ap- 

 pearance. Habitat, Pacific Ocean soundings : H. H. Chase. Plate 1. Fig. 5, illustrates this beau- 

 tiful and peculiar species, but does not show the radiant striatum on surface of valve, which, how- 

 ever, is similar to that on other species of Podosira. 



Solium cv< II I pin m. Heiberg, var. penta^oiiali*. Ivitton. The normal Diatom is 

 described by Heiberg, in his Conspectus, p. 52, Plate 4. Fig. 10 : the variety with live angles is 

 mentioned by Kitton, in his remarks on the Diatomaceous deposits of Jutland, in the Quekett 

 Club Journal for 1870, pp. 100, 102. Plate 1. Fig. 1<». 



The Genus Solium, with Trinacria and H&miaulus are placed by Heiberg in his Danish Con- 

 spectus (i860) among the " HemiaulidcE genuince :" the diagnosis of Solium is here given : " Out- 

 line of valve regularly quadrate or rhomboid : frustule in front view with horn-like processes at 

 the corners, terminating with the spines.'* The diameter of the five-angled variety, as shown in 

 our figure, is .0012 inch, and the distance between the processes i> .0008 inch. Habitat. Island of 

 Fuur, Denmark. 



Stic , tO€li*c , ii!* fwrevilleaiius, N. Sp., W. C. Walker. Valve large, slightly triangular: 

 sides very convex: entire surface granulose, granules disposed irregularly on inner two-thirds of 

 valvular surface : arranged in close radiant rows on outer third: distance between angles .0048 

 inch. Plate 1. Fig. 4. Habitat. Barbadoes. W. C. Walker. 



This very elegant and interesting Diatom is well delineated in the figure: its structure is 

 most decidedly that of Stictodiscus, and could be referred to the Genus Pseudo-Siiciodiscits, insti- 

 tuted by Grunow for the reception of the following forms: 



Pseudo-Stictodiscus angulatus, (Stictodiscus) ; 



Ps. — St. Eulensteinii (Triceratium); 



Stietocli*!'!!* Iiiilen*teiiiii, (Grunow.) H. H. Chase. A representation of this 

 species is given in our Plate 1. Fig. 7: diameter of valves from .0055 inch to .0070 inch. 



