Frustules globose, concatenate; valve simply punctate. LYSIGONIUM MONILIFORME (MUELL.) LINK 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). _Conferva moniliformis_ Mueller (1783). {17}_Conferva nummuloides_ Eng. Bot. pl., 2287, not Dillwyn. _Meloseira borreri_ Grev. _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. Pl. 1, Fig. 7. LYSIGONIUM VARIANS (AG.) DE TONI 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. _Meloseira varians_ Ag. Fresh water. Common in ditches and springs. Pl. 1, Figs. 18 and 19. HYALODISCUS EHR. (1845) (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. ANALYSIS OF SPECIES Valves divided into sectors stelliger Valves not divided but interrupted by short dark lines at intervals radiatus Valves with very fine puncta scoticus HYALODISCUS STELLIGER BAIL. 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. _Podosira maculata_ Wm. Sm. Blue clay. Not common. Pl. 1, Fig. 22. HYALODISCUS RADIATUS VAR. ARCTICA GRUN. 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. _Pyxidicula radiata_ O'Meara. The Philadelphia form corresponds exactly to Grunow's variety which has closer puncta than the type form. Blue clay. Rather rare. Pl. 1, Fig. 21. {18}HYALODISCUS SCOTICUS (KUETZ.) GRUN. Valve small, with puncta about 24 in 10 µ, appearing hyaline. De Toni remarks that it resembles a small form of H. subtilis which occurs north and south of our limits and is yet likely to be recorded. _Cyclotella scotica_ Kuetz. _Podosira hormoides_ Wm. Sm. Blue clay. Not rare. Pl. 1, Fig. 20. Endochrome in the form of four flaps or patches bound together about a common pyrenoid. In H. subtilis numerous rod-shaped chromatophores lie in a row and are not bound in the centre (Mereschkowsky). STEPHANOPYXIS EHR. (1844) em. GRUN. (1884) (stephanos, a crown, and pyxis, a kind of vase or box)