Pediastrum tetras, and P. heptactis are both common.
{{{1}}}„ pertusum. Intestines of the frond hyaline; some of the inner cells are gone, therefore the foraminal appearance is uncertain. The rectangularity of the outer row of cells and the shape of the notch point to pertusum. On the other hand, the number of rows, and the number of circumferential cells, might lead one to infer a new species. On careful comparison, however, I am inclined to consider it as an unusually large specimen of P. pertusum. Number of rows, five; number of cells in inner circle, five. The two next rows are broken down. The fourth circle contains apparently eighteen, and the outer one—the fifth—twenty-one cells. Fig. 9.
Pediastrum, sp. n. Frond square, divided into four equal lobes by a crucial hyaline division. Lobes divided into segments by a deep narrow notch, which extends from the four corners towards the centre of the frond, the segments again partially subdivided by a broad shallow notch. Side view, four cells placed end to end, the central ones about twice the size of the terminal. Although at first sight so very unlike, there is a remarkable similarity between this plant and P. tetras; in fact, the only point of difference consists in the secondary segmentation of the lobes. Fig. 10.
Scenedesmus quadricauda. I have placed before you a figure of this Desmid, because it shows the unusual phenomenon of a broad well-defined coating of hyaline matter external to the cells, and further that the bristles are appendages of the investing coat and not of the cells themselves. Fig. 11.
Diatomaceæ.
Meridion constrictum, H., xcvi.; M. Dic., 12.
Diatoma elongatum, H., xciv.
{{{1}}}„ vulgare, H., xciv.; M. Dic., 12.
{{{1}}}„ grande, M. Dic.
Melosira.
Campylodiscus costatus, M. Dic., 12.
Surirella bifrons, M. Dic., 13.
Synedra splendens, H., xcvii.
Cocconeis placentula.
Navicula.
Gyrosigma macrum, M. Dic., 11.
{{{1}}}„ attenuatum, M. Dic., 11.
Pinnularia oblonga, M. Dic., 11.
Stauroneis phœnicenteron, M. Dic, 11.
Encyonema.
