Frustules quite robust, with diam. several times the length, deeply furrowed at the margin, areolate and punctate. Valve with radiating striæ disappearing toward the centre, and with a double row of cells near the margin, the outer one having the appearance of a crown of teeth. _Gaillonella sulcata_ Ehr. _Paralia sulcata_ (Ehr.) Cleve. _Paralia marina_ Heib. {16}Marine and brackish. Common in all parts of the world, and fossil in the Miocene. The Philadelphia form is the var. genuina Grun. Pl. 1, Figs. 11 and 12. In a gathering from Media of Meloseira crenulata (Palmer leg.), occasional filaments are noticed with much longer and narrower frustules which become enlarged in the middle and are seen to contain inner frustules in the process of still further division, as shown in Fig. 2, Pl. 38. Meloseira dickei Thwaites shows internal box-like cells placed one within the other, which were supposed by Thwaites to be a method of reproduction. Wm. Smith doubts this, but is unable to offer any explanation. In the present form the mode of reduplication is that usually found in filamentous forms, but in this case the presence of perfect frustules enclosing others in the process of still further division has been heretofore unfamiliar to me. The swelling in the middle appears to indicate that not all filamentous diatoms are reduced in size by subdivision. In outline the valve is like that of a "truncated cone," as described by Petit in referring to Gaillonella granulata var. bambusina Petit (Diat. Nouv. et Rares, Jour. de Micrographie, 1890). GAILLONELLA BORY DE ST. VINCENT (1823) (named after Gaillon, a botanist of Dieppe) Frustules ellipsoidal, united in long filaments, usually found in pairs; each valve is furnished with a circular collar or crest extending at right angles to the convex edge. Valve hyaline at the centre from near which radiate lines of fine puncta, 18-20 in 10 µ. NOTE.--The original names of both Meloseira and Gaillonella are retained, as there is no good reason for contracting the Greek diphthong in the first, and the second is the correct spelling. GAILLONELLA NUMMULOIDES (DILLW.) BORY Frustules as in the generic diagnosis. Diam. 30 µ. _Conferva nummuloides_ Dillwyn (Brit. Confervæ, p. 45, Sup. Pl. B). _Meloseira nummuloides_ Ag. Heiberg and O'Meara assign this species to _Lysigonium moniliforme_ (Muell.) Link, which is not keeled. While Dillwyn's and Lyngbye's figures do not show the keel, it is probable from their descriptions that the angular outline produced by the keel was noticed. Marine or brackish. Coast of New Jersey; Hudson River (Bail.). Pl. 1, Figs. 13 and 14. _Gaillonella moniliformis_ of Bailey is this form, as he describes it as having "two minute projections of the delicate transverse ridges seen near the ends of the two globules belonging to a joint." (Amer. Jour. Science, 1842, p. 89, Pl. 2, Fig. 3.) LYSIGONIUM LINK (1820) (luo, to loose, and gonu, a joint)