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.
Frustules as in the generic diagnosis. Diam. 30 µ.
_Conferva nummuloides_ Dillwyn (Brit. Confervæ, p. 45, Sup. Pl. B).
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.).
_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.)
Frustules globose, concatenate; valve simply punctate.
Frustules usually in twos, not keeled; valve with puncta in longitudinal lines, the puncta of the enveloping zone larger and in transverse rows. L. 25-40 µ (De Toni).
{ 17}_Conferva nummuloides_ Eng. Bot. pl., 2287, not Dillwyn.
_Lysigonium nummuloides_ (Lyngb., Kuetz.) O'Meara = _Gaillonella nummuloides_ (Dillw.) Bory. See O'Meara, p. 248.
Marine and brackish. Long Island Sound and coast of New Jersey.
Frustules cylindrical, in long filaments, slightly constricted on each side of the suture; puncta in oblique rows in zone view. Valves 15-35 µ in diam. (De Toni), sub-plane, with fine puncta in lines radiating from the centre. Under medium magnification the frustules appear smooth. Very variable in size.
Fresh water. Common in ditches and springs.
(hyalos, transparent, and discus, a disc)
Frustules spheroidal; valve with a flattened, irregularly punctate umbilicus from which proceed radiating or decussating lines of fine puncta.
Valves not divided but interrupted by short dark lines at intervals radiatus
Valve with puncta in oblique decussating rows which, by reason of the difference in obliquity, form numerous sectors. Umbilicus irregular, with scattered, coarse puncta. Margin wide, striated.
Valve with radiating puncta from a rather small umbilicus, the rays interspersed with short, dark lines, having the appearance of spines, at irregular intervals. Margin broad, striated.