These were middens, the accumulated refuse of coastal communities who ate oysters, cockles, limpets, periwinkles, and razor shells over what must have been a considerable stretch of time. A midden is essentially an ancient rubbish heap, the kind of deposit that archaeologists prize precisely because it preserves the mundane details of daily life: what people ate, how they cooked, what animals they kept or hunted. The two at An Teanach were, by any standard, unusually substantial.

The scholar T. J. Westropp recorded them in the Journal of the Royal Society of Antiquaries of Ireland in 1914, noting that each mound stood over ten feet high and that the deposit itself was four to five feet thick, composed of burnt stones, black mould, charcoal, shells, and broken bones. He placed them in a hollow beside what was already, even then, a nearly vanished old track, and included a sketch plan marking their approximate position. That description gives some sense of how marginal the location already felt a century ago, a hollow off a fading route in a remote part of north Mayo. When an inspection was carried out in 1995, no trace of the middens could be found. Whether they were quarried away, absorbed into agricultural land, or simply eroded and dispersed is not recorded.