New Diatoms from Honduras. Described hj A. Grunow. 185 
The peculiar structure of the connecting membrane in Triceratium 
orbiculatum var. elongatum and Cerataidus lasvis, bears, in my 
opinion, only a superficial resemblance to Ehizosolenia. This genus 
resembles Ehabdonema and some allied genera in possessing a series 
of annuli (generally more or less wedge-shaped), and at a certain 
period of growth a smooth connecting membrane is formed, and 
shortly after two beaked ends (valves) are produced ; in some 
splendid specimens of B. striata from the Arafura Sea this has 
occurred three or four times before the frustules separated, thus 
forming a filament of considerable length. 
It seems to me probable that Mr. Thwaites’ explanation of the 
peculiar state in which Orthosira Dickiei is sometimes found is 
correct, and that it is a sporangial condition. In a very good 
gathering of this form I have seen it in every stage, from its com- 
mencement to the reproduction of the normal frustule ; the first 
indication is the formation of two conical valves, resembling two 
thimbles joined at their bases ; within these are formed two fresh 
valves with the bases slightly broader ; this is repeated until a large 
but normal frustule is formed, and self-division goes on until the 
EXPLANATION OF PLATES. 
Plate CXCIII. 
Fig. 1 .—Licmophora Remulus. a, valve; 6, frustule X 400. 
„ 2 . — Asterionella Bleakeleyi var. ? a, valve ; 6, frustule X 400. 
„ 3 . — Synedra Icevigata x 900. 
„ 4. — „ „ var. obtusiuscula x 900. 
„ 5a, b . — „ „ „ ? hyalina x 900. 
„ 6. — „ provincialis x 900. 
„ 7. — „ „ var. tortuosa X 900. 
„ 8. — a, „ undosa x 400 ; b, apex ; c, centre x 900. 
„ 9. — a, „ cornigera x 400 ; b, apex ; c, centre x 900. 
„ 10. — a, „ Frauenfeldii x 900; b, apex; c, centre x 1540. 
„ 11. — a, „ crystallina var.? insignis X 200; b, apex; c, centre X 900. 
„ 12. — „ „ var. bacillaris. a, valve X 450 ; 6, apex ; c, centre x 900. 
Plate CXCIY. 
Fig. 1 . — Synedra Baculus var. minor x 900. 
„ 2. — „ capillaris X 900. 
„ 3 . — Sceptroneis cuneata x 400 ; b, apex ; c, centre ; d, lower apex x 900. 
„ 4. — „ dubia X 900. 
„ 5 . — Striatella Lindigiana. a, valve ; b, frustule x 400 ; c, areolation x 1500. 
„ 6 . — Striatella intermedia, a , valve ; b, frustule x 400. 
„ 7. — „ unipunctata. a, valve x 900; b, portion of ditto x 1540. 
„ 8 . — Plagiodiscus Martensianus x 900. 
„ 9a. — „ nervatus X 400. 
„ 96. — „ „ forma minor x 900. 
„ 10 . — Nitzschia Kolaizeckii x 900. 
„ 11 . — Bacillaria paradoxa var. tropica x 400. 
„ 12 . — Mastogloia erythraea x 900. 
„ 13. — „ „ var. x 900. 
„ 14.— „ „ „ x 900. 
„ 15. — „ „ „ biocellata x 900. 
[Plate CXCV. 
