The posthumous paper by J.A. Wright on gully pattern and development is a valuable contribution to the study of these interesting geomorphic features. In December 1963 1 had several stimulating discussions with Dr. Wright on the origin of the gullies and their rather persistent orientation almost perpendicular to the coastline. The gullies strongly reminded me of grooves and surge channels on coral reefs in Hawaii, which I had studied earlier that year. The rounded pot-holing illustrated inPlate V of the paper, also occurs on reefs.
An adjustment should be made to the observations recorded in Wright's Section 8: "Comparison with Bikini Grooves and Surge Channels",where the average wave periods off 42G are quoted as 26 and 18 seconds.
In November 1963, I made a number of observations along the same coast (SWA) and found that the wave period averaged between 8 and 9 seconds. I also noticed that the methodology used by Dr.Wright's observer resulted in omission of one or more waves if they did not break along the same line as their recorded predecessor. This is clear from inspection of the averages which are near multiples of 9 seconds. The corrected wave periods fit the formula of Munk and Sargent (1948) and confirm its applicability to the SouthWest African gullies.
Although deeply shocked by Dr. Wright's drowning while participating in one of our underwater studies, we have continued diving investigations of the sea floor and have since recorded scattered occurrences of submerged surge channels in water depths ranging to 100 feet along the entire coast between Oliphants River and Walvis Bay. Only one of the channels inspected under water, however, was as spectacular as those figures in Plate V and VI.
In conformity with Dr. Wright's observations, we found that the trends of the gullies are commonly discordant with the regional structural trends in the predominantly schistose bedrock and that they are generally oriented perpendicular to the coastline.Dr .Wright's conclusion that cobbles and boulders have been the chief abrasive agents in the formation of gullies is supported by the fact that the channels we explored almost invariably contained these coarse materials.

Munk, W . H . and Sargent, M. C . (1948): "Adjustment of Bikini Atoll to Ocean Waves" Trans.Amer.Geophys.Union, 29, p.855-860
Wright , J.A. (1965):"Gully Pattern and Development in Wave-cut Bedrock Shelves North
of the Orange River Mouth,South West Africa." Trans.Geol.Soc.South Africa, v.LXVI, p.1-9