48 
Wallich, on Siliceous Orga7iisms. 
assumed by the rays in these diatoms ; the rays in the first 
being almost rhomboidal^ whilst those in the second are 
almost linear. The figures clearly prove that the so-called 
"umbilical rays^^ are merely the sutures of the bases of 
the rays. 
Fig. 13, var. /3. Diameter -0015. 
Pig. 14, var. \. Diameter -0019. 
Bay of Bengal, Indian Ocean. From Salpse. 
Chcetoceros bacteriastrium, n. sp. — Filament cylindrical. 
Valves more or less cup-shaped, discoidal. With from four 
to twelve marginal awns. 
The valves in this species resemble Mr. Shadbolt^s genus 
Bacteriastrium so closely, as to leave no doubt of both belong- 
ing to the same form. The varieties are very numerous, but 
differ only in number of awns, and their simple or furcate 
character. Size extremely variable. 
Very frequent and abundant. 
Atlantic. From Salpse. Figs. 16 and 17. 
Chcetoceros boreale, Bailey. — This form is figured in order 
to show the cup-shaped structure of the valves, and the 
cylindrical connecting zones. 
Very frequent. 
Atlantic. From Salpse. Fig. 18. 
Triceratium punctatum, n. sp. — Valve with a minute horn 
at each angle, and a line of marginal puncta. Cellulation 
minute, radiating from centre. Diameter '0012 to 'OOIS. 
Fig. 21. 
Bay of Bengal, Indian Ocean, Atlantic. From Salpse. 
Frequent. 
Coscinodiscus radiatus, Ehr. — A small variety, with a 
crenate border within the margin. Diameter '0010. Fig. 22. 
Bay of Bengal, Indian Ocean. From Salpse. 
Synedra doliolus, n. sp. — Frustules linear, frequently form- 
ing a cask-shaped group, by their adherence after division. 
Valve sub-arcuate. Pseudo-nodule absent. Strise 30 in 
•001. Length -0020 to -0050. 
Bay of Bengal, Indian Ocean, Atlantic. From Salpae. 
Common. Fig. 19. 
This form is unquestionably a free species, and may be 
placed under Synedra provisionally. 
Nitzschia lanceolata, Sm. — A variety with the strise ar- 
ranged in quincunx, what nnder certain aspects gives the 
appearance of oblique striation. Length '0060 to '0075. 
Strise 48 in '001. 
Bay of Bengal, Indian Ocean, Atlantic. From Salpse. 
Frequent. Fig. 20. 
