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.
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)
Frustules ellipsoidal, concatenate; valves tumid, of unequal convexity, coarsely areolate, the cells in rows parallel to the longitudinal axis, not radiate, with stray spines or teeth placed concentrically more or less near the margin.
According to Karsten the chromatophores are round or angular discs which lie near the connective zone.
STEPHANOPYXIS TURRIS (GREV.) RALFS
Valve cylindrical, with a crown of stout spines less than the diameter of the valve near the margin. Cells hexagonal, about 2 in 10 µ, sometimes punctate. The valve having the greater convexity has the larger spines, though usually less of them.
Creswellia turris Grev. (Gregory, Diat. of the Clyde, T. R. S. E., vol. 21, part 4, p. 66.)
Stephanopyxis appendiculata Ehr.?
Creswellia is incorrectly based, as stated by Ralfs, on the concatenation of the valves which was not noticed by Ehrenberg in the fossil forms. It had been suggested by Kuetzing in Systema Algarum (p. 126).
Blue clay. Port Penn and Smith's Island.
Pl. 2, Figs. 1 and 2.
STEPHANOPYXIS CORONA (EHR.) GRUN.
Valve larger than in turris, sub-globose, coarsely areolate cells, 4-5 in 10 µ. One valve furnished with a crown of teeth shaped like the letter T and united at the top into a ring above the margin of the valve; the other valve with long spines more or less concentrically arranged.
Blue clay. Not common. Fossil in the Nottingham deposit.
Pl. 2, Fig. 3.
Note.-The diatomaceous deposit, so often called "Bermuda" or "Bermuda tripoli," especially by foreign writers, is in reality the Miocene stratum extending for miles along the Patuxent River near the village of Nottingham, Md. The author is perfectly familiar with the location, having made large collections there. The mistake in the name is due to the fact that Prof. Bailey received material from Mr. Tuomey marked "Bermuda Hundred," which is located near Petersburg, Va. Attempts have been made to find material there and while there is an earth containing Miocene diatoms at Petersburg, it does not exactly correspond to the material sent to Ehrenberg by Bailey, who was in doubt as to the locality. The Bermuda Islands are of coral formation and have no deposits of diatomaceous earth.
Pyxidicula Ehr. (1833)
(dim. of pyxis, a box)
Frustules globular, solitary or in short fasciæ. Valve more or less hemispherical, areolate, destitute of spines.
PYXIDICULA CRUCIATA EHR.
Valve hemispherical, with large, hexagonal cells. An inner stratum is finely punctate.
Blue clay. Walnut St. Bridge. Rare.
Pl. 38, Fig. 8.
This form is not usually described as having punctate areolæ, but it does not apparently differ from other forms of Pyxidicula of Ehrenberg as described by Kuetzing (Species Algarum, pp. 21-23), including P. areolata. In fact, it differs from Stephanopyxis, which is also sometimes punctate, only in the absence of spines. In fossil deposits the absence of an easily detached stratum is not significant. The difference, except in size, between it and P. mediterranea Grun. (V. H. S., Pl. 95, Figs. 15 and 16), I am unable to determine.
Although many species of Meloseira are fresh-water, the habitat of the group Meloseirinæ is, in general, marine. It more nearly coincides in structure and development with other algæ not diatomaceous, the siliceous envelope constituting its most distinctive feature. As we proceed in the classification, the structure both of the frustule and contents becomes more complicated.
(b) COSCINODISCINÆ
1. Cyclotella.-Valve with two concentric divisions of different structure, one a wide border and the other a central surface.
2. Coscinodiscus.-Valve areolate or punctate, with a narrow border of the same structure.
Cyclotella Kuetz. (1833)
(cyclos, a circle)
Frustules single or geminate, cylindrical, short, in zone view rectangular or with undulating sides. Valve usually with smooth or punctate striæ, centre sometimes bullose, smooth, or with granules scattered or radiating.
Chromatophores numerous along the valves (Pfitzer).
CYCLOTELLA STRIATA (KUETZ.) GRUN.
Valve 30-80 µ in diam., with coarse striæ, 7-12 in 10 µ, centre coarsely punctate and bullose.
Coscinodiscus striatus Kuetz.
Cyclotella dallasiana Wm. Sm.
Common in the blue clay.
Pl. 2, Fig. 9.
CYCLOTELLA MENEGHINIANA KUETZ.
Frustule in zone view rectangular, undulated; valve, 10-20 µ in diam., marginal striæ robust and transversely punctate, centre radiately punctate.
Cyclotella kuetzingiana Wm. Sm. (not Thwaites).
Crum Creek.
Pl. 2, Fig. 8.
CYCLOTELLA MENEGHINIANA, VAR. STELLIGERA CL. AND GRUN.
Differs from the type in the coarse radiating lines at the centre.
Broomall Lake, Media.
Pl. 2, Fig. 4.
CYCLOTELLA MENEGHINIANA, VAR. STELLULIFERA CL. AND GRUN.
As in type but with the central rays granulate.
Broomall Lake, Media.
Pl. 2, Fig. 12.
CYCLOTELLA STYLORUM (BR.?) V. H.
Margin striated, the alternate striæ thickened near the border, producing an appearance of subquadrate cells. Centre faintly granulate, the outer border of which is encircled by 10-12 puncta, each of which is surrounded by a small hyaline space.
Blue clay. Rare.
Van Heurck gives this form doubtfully as a variety of striata, while De Toni makes it synonymous with it. Van Heurck's figure is not that of Brightwell, but as the specimen above described is, I believe, exactly the same as Van Heurck's, I retain his name.
Pl. 2, Fig. 10.
CYCLOTELLA COMTA (EHR.) KUETZ.
Valve with marginal striæ well marked, each third or fourth costa more robust than the others. Central part finely striated, the striæ punctate, radiating.
Fresh water.
Pl. 2, Fig. 7.
The form here figured is probably the variety radiosa Grun. and is from a New England specimen. It is quite likely to occur in this locality.
CYCLOTELLA OPERCULATA (AG.) KUETZ.
Frustules in zone view undulated. Angles rounded. Marginal costæ alternating with minute spines; centre nearly smooth, depressed, convex or flexuose.
Fresh water.
Pl. 2, Figs. 5 and 6.
The figure is drawn from a specimen from Boston, Mass., H. L. Smith Type Slide No. 107, marked equivalent to C. minutula Wm. Sm.
CYCLOTELLA ANTIQUA WM. SM.
Marginal...
