(amphora, a jar) Valves asymmetrical along the longitudinal axis, as in Cymbella, but with the plane passing through the dorsal and ventral sides of one valve at an angle with that of the other. As Cleve states, Cymbella and Amphora are forms of Navicula "with both valves similar and asymmetrical along the longitudinal axis," and the difference between Cymbella and Amphora is in the "degree of asymmetry." If, following H. L. Smith's diagrams (Lens, Vol. 2, 1873, p. 66), we assume that the usual form of the valve in Navicula is elliptical or lanceolate, and the zone view is rectangular, we have in Cymbella an arcuate median line and a more or less reniform valve, while the zone view remains rectangular with the valves parallel. Now, if the valves are asymmetrical along the longitudinal axis, and one side of one valve is separated from the corresponding side of the opposite valve by a wider connective zone than is the case on the other side, the transverse section of the frustule will appear cuneate, as in Amphora, and the connective zone will be wider on one side than the other. When, therefore, we examine an entire frustule as it is usually seen, we shall find the two raphes of the valves in focus at the same time on the ventral side, and, by changing the focus, the convex sides of the same valves are seen, the dorsal view with, usually, a wider connective zone. As an illustration, compare Figs. 5 and 6, on Plate 15, Fig. 6 being the ventral, and Fig. 5 the dorsal view. As Amphoræ are epiphytic or parasitic, they are considered, as Cleve remarks, like Achnanthes and Cocconeis, as "degenerated forms." Chromatophores usually single, lying on the ventral connective zone. Mereschkowsky describes nine forms. Cleve divides the genus into a number of groups as follows: _Amphora proper._--Connective zone not complex; valves with longitudinal lines on the dorsal side; coarsely punctate or costate. _Diplamphora._--Zone complex; otherwise as in Amphora. _Halamphora._--Longitudinal lines absent; frustule elongate, with protracted ends. {65}_Oxyamphora._--Zone complex; longitudinal lines absent; frustule elliptical; valve lunate, with or without a central stauros; striæ punctate. _Amblyamphora._--Zone complex; frustule rectangular; valve lunate; striæ punctate; axial and central areas indistinct. _Psammamphora._--Zone not complex; frustule rectangular; central nodule frequently dilated to a stauros; no axial or central area. _Cymbamphora._--Valve semi-lanceolate; median line straight, approximate to the ventral margin. AMPHORA AMPHORA ROBUSTA GREG. Frustule elliptical, truncate; valve lunate, with straight ventral margin; median line biarcuate; ventral side with coarse, radiate striæ, 6 in 10 µ, on both sides of the median line. Along the coast. Pl. 15, Fig. 1. AMPHORA PROTEUS GREG.