FIGURE 2. (Station T1-9, photo 43) Location about 50 feet from photo shown in Figure 1, same depth and position. The dark color of the rocks may be due to a coating of manganese dioxide. However, the rocks may actually be composed of dark material; no dredgings were taken here. All dredgings from Mid-Atlantic Ridge have brought up basalt and in some cases also gabbroic and serpentinized rock. It seems likely that the rock in Figure 2 and 3 of this plate is basalt. Note the abundance of sessile life on the rocky areas in contrast to its absence in the gravel-covered areas. FIGURE 3. (Station T1-9, photo 45) Location about 100 feet from photo shown in Figure 2, same depth and position. Rock bottom on the Western Rift Mountains, Mid-Atlantic Ridge. FIGURE 4. (Station V4-7, photo 27) Depth 500 fathoms, location 37° 25´N., 31° 10´W., Western Rift Mountains, Mid-Atlantic Ridge, south of the Azores Plateau. FIGURE 5. (Station T1-54, photo 15) Depth 2100 fathoms, location 23° 07´N., 43° 45´W., Upper Step (eastern side), Mid-Atlantic Ridge. Apparatus in lower right attached to camera. Note tracks of crawling animal in left side of photo and small holes in bottom sediment. Photograph contrasts sharply with those from Rift Mountains in lack of current or oscillation ripples and rock outcrops. FIGURE 6. (Station T1-14, photo 6) Depth 2130 fathoms, location 46° 04´N., 17° 43´W., Lower Step (eastern side), Mid-Atlantic Ridge. Note fecal pellets, mounds, and small holes. Again lack of evidence of strong currents or outcrops is notable. Positions of stations shown on Plate 30] Photographs of the seamounts generally show winnowed and rippled sediment and rock (Pl. 15). Virtually all loose sediment is being removed from the seamounts. The horseshoe, open to the east, encloses an abyssal plain which is, judging from the sea-floor gradients, fed largely from the east by turbidity currents originating in the Straits of Gibraltar and the Gulf of Cadiz areas. MILNE SEAMOUNT: Early charts of the western Atlantic showed an extensive bank of 20,000 square miles rising from the center of Newfoundland Abyssal Plain. At about the center of this area an exceptionally high peak has been discovered by cable ships, and the old name Milne Seamount has been assigned to this peak. It rises more than 2500 fathoms above the abyssal floor. Two seamounts of similar size have been found north and south of the Milne Seamount by workers on the R. V. ATLANTIS (Fig. 30). As the abyssal floor is better surveyed many more isolated seamounts will undoubtedly be discovered, and they may reveal tectonically significant patterns. SEISMICITY OF THE OCEAN-BASIN FLOOR