The Diatomaceæ of Philadelphia and Vicinity

Section 1. Himantidium

EUNOTIA MAJOR (WM. SM.) RAB.

Valve arcuate, linear, subcapitate, recurved. Striæ punctate, 12 in 10 µ L. 90-190 µ.

Common in fresh water.

Pl. 13, Figs. 1 and 2.

EUNOTIA GRACILIS (EHR.) RAB.

Valve with sides parallel; apices slightly capitate and revolute; striæ, 10 in 10 µ. The striæ on the connective membrane more delicate than in E. major. Intermediate forms occur.

Common in fresh water.

Pl. 13, Fig. 3. Fig. 4 is indeterminate.

EUNOTIA NYMANNIANA GRUN.

Valve small, curved, with parallel dorsal and ventral margins; apices truncate and recurved into dorsal elevations; striæ delicate.

Blue clay. Not common.

Pl. 13, Fig. 32.

{52}EUNOTIA PECTINALIS (KUETZ.)

Valve linear, arcuate, apices slightly rostrate; striæ distinctly punctate with puncta in longitudinal rows nearer together at the ends.

Himantidium pectinale Kuetz.

Common in fresh water.

Pl. 13, Figs. 6 and 7.

The fasciæ are associated in large masses, sometimes an inch or more in diameter, and late in August are found a foot or more in length, of a beautiful chocolate color. Exceedingly abundant in the cedar-swamp streams of the Pine Barren regions of New Jersey. In winter, the dead frustules form a parchment-like coating upon the twigs, dead leaves, and other débris on the borders of streams.

This species can scarcely be referred to Dillwyn's Conferva pectinalis, as, in his description, quoting Mueller, he says that "the filaments are of a dirty green color; seldom exceeding half an inch in length." Dillwyn's form is probably Fragilaria virescens, which equals Fragilaria pectinalis Ehr., while Kuetzing's species is Fragilaria pectinalis Ralfs. It is not impossible to confuse Fragilaria virescens and Eunotia pectinalis when the zone only is seen under a low power and their mode of growth is similar.

EUNOTIA PECTINALIS VAR. UNDULATA RALFS

Valve as in type form, but with undulate margins.

Common in the cedar swamps of New Jersey.

Pl. 13, Figs. 8 and 10.

EUNOTIA PECTINALIS VAR. SOLIEROLII (KUETZ.)

Valve as in type, but with internal divisions as though in the process of reduplication.

Not common. Moorestown, N. J. (Palmer).

Pl. 13, Fig. 9.

EUNOTIA PECTINALIS VAR. VENTRICOSA GRUN.

As in type, but with the valves tumid in the middle.

May's Landing, N. J.

Pl. 13, Fig. 12.

Fig. 11 is a form found in the blue clay. It differs in the coarser puncta from the var. ventricosa. In outline it resembles Eunotia arcus Wm. Sm., which is Ceratoneis arcus (Ehr.) Kuetz., but the central nodule is not present as in the latter form, which connects Eunotia and Cymbella. It may be a form of E. luna Ehr. (A. S., Atlas, Pl. 286, Figs. 33 and 34.)

EUNOTIA VENERIS KUETZ.

Valve with convex dorsal and straight ventral margins, more or less constricted near the sub-acute apices. Striæ subtle, punctate.

Eunotia incisa Greg.

May's Landing, N. J. Blue clay, Pavonia, N. J.

Pl. 13, Figs. 30 and 31.

{53}EUNOTIA (PROPER)

EUNOTIA LUNARIS (EHR.) GRUN.

Frustules sessile, solitary or in clusters. Valve arcuate, narrow, attenuated toward the apices, which are sometimes slightly rostrate or rostrate-capitate; transverse striæ, 14 in 10 µ, punctate.

Very common in ditches, especially in the spring. Variable in length.

Pl. 12, Figs. 24 and 25.

EUNOTIA HEMICYCLUS (EHR.) RALFS

Valve semicircular, with obtuse apices; striæ transverse, punctate; terminal nodules minute and indistinct.

Hammonton Pond, N. J. Rare.

Pl. 12, Fig. 23.

The genus Pseudo-Eunotia was created by Grunow for forms like Eunotia, but without terminal nodules. As, however, in E. lunaris and E. hemicyclus nodules are evident, although not so large as in many species, I include these two forms as heretofore under Eunotia.

EUNOTIA BICEPS EHR.

Valve linear, slightly arcuate, narrow, with rounded apices somewhat revolute; striæ, 16 in 10 µ.

May's Landing, N. J.

Pl. 13, Fig. 27.

EUNOTIA PRÆRUPTA EHR.

Valve convex on dorsal side, apices dilated and truncate; striæ distant at centre.

Common in the blue clay.

Pl. 13, Fig. 5.

EUNOTIA PRÆRUPTA VAR. BIDENS GRUN.

Valve with two undulations; otherwise as in type.

Eunotia bigibba Greg.

With the type.

Pl. 13, Fig. 19.

EUNOTIA ROBUSTA RALFS

Valve arcuate, with several or numerous dorsal ridges or crenæ which decrease in relative size in proportion to their number. Striæ radiate, variable in distance apart, and in size of puncta.

Ralfs included under this one name the following species named by Ehrenberg: E. diodon (2 crenæ); E. triodon (3); E. tetraodon (4); E. pentodon (5); E. diadema (6); E. heptodon (7); E. octodon (8); E. enneadon (9); E. decadon (10); E. hendecadon (11); E. duodecadon (12); E. serra (13); E. prioritis (14); all more than 20, E. polyodon. E. scalaris, with from 15 to 17 crenæ, and E. icosodon with 20, may be added.

It is probable that all of these forms occur at May's Landing, N. J. The forms with more than eight crenæ are comparatively rare. In the blue clay those with from four to six are most common.

Pl. 13, Figs. 13, 14, 15, 16, 17, 21, 24, 25.

{54}EUNOTIA BACTRIANA EHR.

Valve linear, apices revolute, acute, dentate on the dorsal margin, with one acute crena near each end.

Tom's River, N. J. Rare.

Pl. 13, Fig. 18.

EUNOTIA BIDENTULA WM. SM.

Valve with straight ventral margin, and with two undulations on the dorsum; apices large, rounded.

May's Landing, N. J. Rare.

Pl. 13, Fig. 20 (not Schumann's form, which has angular crenæ).

EUNOTIA FORMICA EHR. VAR.?

Valve turgid in the middle and at the apices which are unilaterally truncate.

Pensauken, N. J. (artesian well).

Pl. 13, Fig. 26 (not a typical form).

The following are forms which appear to be indeterminate, or, in any case, are scarcely worthy of distinction by specific names, as might be said of others of the innumerable variations of this genus:

Fig. 23, Pl. 13, probably a form of prærupta. Newtown Square.

Fig. 28, Pl. 13, from the blue clay.

Fig. 29, Pl. 13, an asymmetrical form, apparently abnormal, but not rare at May's Landing, N. J.

Fig. 17, Pl. 38. Valve convex on the dorsal side, incised on the ventral; striæ about 15 in 10 µ, closer at the ends; L. 30 µ. Schuylkill River.

Fig. 18, Pl. 38. Valve arcuate, asymmetrical, broader at one end; terminal nodules large; striæ, 10 in 10 µ; L. 47 µ. Gloucester, N. J., artesian well.

Numerous variations of the above species are illustrated in Schmidt (Atlas, Pls. 285-291).

ACTINELLA LEWIS (1865)

(dim. of actin, a ray)

Frustules solitary, or in small clusters, sub-cuneate or nearly linear. Valve arcuate, rounded at one end and suddenly widened at the other into a cup-shaped or lychnoid inflation.

ACTINELLA PUNCTATA LEWIS

Valve with fine, transverse striæ; on the margin, puncta at intervals; terminal nodules distinct.

May's Landing, N. J.

Pl. 12, Figs. 16, 17, 18.

Fig. 17, from Tom's River, N. J., is an approach toward A. brasiliensis Grun.

Fig. 18 represents the frustules geminate, a frequent occurrence.

{55}NAVICULOIDEÆ

In discussing the Naviculoid group, the general divisions of Cleve are here followed, and all diatoms having a true raphe are included. I have added the genus Epithemia and also Rhopalodia, partly because they contain a raphe of a certain kind and partly because they resemble the markings of certain of the genus Hantzschia in the following group, although in other respects there is probably no similarity.

The difficulty of combining the numerous genera into groups which are naturally affiliated is avoided in the following arrangement based on superficial similarities, and is intended merely as an artificial key. To unite all forms having a raphe and which are symmetrical with valves similar and not sigmoid, under the one genus Navicula, as has been the custom previous to the publication of Cleve's monograph, would result in associating species differing in so many respects in relation to structure of the valve and cell contents that it seems advisable to retain the new genera, especially as the original genus is likely to be still further reduced when more is known of the structure and life history of the group.

KEY TO THE GENERA

Valves dissimilar. Achnantheæ

symmetrical Cocconeis

asymmetrical

to the longitudinal axis Anorthoneis

to the transverse axis Rhoicosphenia

in zone view Achnanthes

Valves similar and asymmetrical

asymmetrical to the longitudinal axis

valves parallel Cymbella

valves not parallel Amphora

valves keeled, twisted (sometimes symmetrical) Amphiprora

valves keeled Tropidoneis

valves reniform and keeled Auricula

median line sigmoid at the ends Scoliotropis

asymmetrical to the transverse axis

striæ punctate and costate Gomphoneis

striæ punctate Gomphonema

Valves similar, symmetrical and sigmoid

striæ oblique Pleurosigma

striæ at right angles Gyrosigma

Valves similar, symmetrical, not sigmoid

striæ punctate, nodules elongated Frustulia

striæ subtly punctate, central nodule forked Amphipleura

striæ punctate and reticulate, in two strata Dictyoneis

striæ punctate and alveolate, in three strata Trachyneis

striæ punctate, in two strata Brèbissonia

striæ interrupted by blank lines Anomoeoneis

striæ crossed by longitudinal lines Caloneis

striæ oblique, median fissures in opposite directions Neidium

striæ punctate and costate, median line with horns Diploneis

striæ punctate; valves separated by septate plates Mastogloia

striæ punctate, central area dilated into a stauros Stauroneis

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