Adventurer Roy Chapman Andrews mentions in an article published in 1922 in the "Asia Magazine" and later in his book "On the Trail of Ancient Man" (1926), a strange creature, said to inhabit the Gobi-desert in Mongolia:
"Then the Premier asked that, if it were possible, I should capture for the Mongolian government a specimen of the allergorhai-horhai. I doubt whether any of my scientific readers can identify this animal. I could, because I had heard of it often. None of those present ever had seen the creature, but they all firmly believed in its existence and described it minutely. It is shaped like a sausage about two feet long, has no head nor legs and is so poisonous that merely to touch it means instant death. It lives in the most desolate parts of the Gobi Desert, whither we were going. To the Mongols it seems to be what the dragon is to the Chinese. The Premier said that, although he had never seen it himself, he knew a man who had and had lived to tell the tale. Then a Cabinet Minister stated that "the cousin of his late wife's sister" had also seen it. I promised to produce the allergorhai-horhai if we chanced to cross its path, and explained how it could be seized by means of long steel collecting forceps; moreover, I could wear dark glasses, so that the disastrous effects of even looking at so poisonous a creature would be neutralized. The meeting adjourned with the best of feeling."
This strange creature (said to be 0,5-1,5 meter / 18 inches - 5 feet long) became popular after 1990, when engineer and self-proclaimed monster hunter Ivan Mackerle (1942-2013) published some articles based on his travels to Mongolia. Today it's best known as "Mongolian Death Worm". Not only poisonous, it seems also to possess a electric organ, as Mackerle reports that a geologist was killed by a high-voltage electrical discharge when he inadvertently touched a buried animal with a iron rod.
Russian paleontologist and pioneering taphonomist Ivan Antonovich Efremov (1908-1972), who also worked in the Gobi-desert, published his scientific adventures in the book "The Wind's Path" (1958), where he mentions the encounter with an elderly man. The man warned the geologists of the death worm, and Efremov was impressed enough of this legend to use the death worm in one of his sci-fi stories, entitled appropriately "Olgo-Khorkho" (the monstrous worm), where a geological expedition is decimated by two of these terrible creatures. It seems however that the hate is reciprocal, as supposedly a geological expedition burned alive a bunch of these beasts in 1948.
German naturalist Eberhard Werner Happel (1647-1690) mentions in his "Relationes curiosae, oder Denckwrdigkeiten der Welt" (Curiosities of the World, published in 1683- 1691) the discovery of another terrifying worm-like creature with a geological connection.
A certain de la Voye observed "on an old stone wall to midday, much of [the] rocks eaten by these worms. The holes were big enough to put a hand within. Such holes were full of living worms and dust, which they made of the rocks.."
Observing the animals under a magnifying glass de la Voye continues:
"This vermin is enclosed in a grey shell, as depicted in Fig.1., large as a grain of barley...on the tip there is a hole for the excrements, on the other end there is a larger hole, through which the head protrudes.
They are entirely black, the body shows various segments, near the head there are three legs, each has two joints, not dissimilar to these of a flea.
When they move their body is suspended in air, the mouth but is still showing towards the rock. The head is bulky, a bit smooth, similar in shape and color to the shell of a snail... also the mouth is similar large, with four, cross shaped teeth … "
Able to munch even rocks, this creature seems to be indeed a geologist's worst nightmare come true.
COLEMAN, L. & CLARK, J. (1999): Cryptozoology A to Z the Encyclopedia of Loch monsters, Sasquatch, Chupacabras, and Other Authentic mysteries of Nature.Fireside Publ. - New York: 270
EBERHART, G.M. (2002): Mysterious Creatures - A Guide to Cryptozoology. ABC-CLIO, Santa Barbara: 723
SHUKER, K.P.N. (2003): The Beasts That Hide from Man: Seeking the World's Last Undiscovered Animals. Paraview Press, New-York: 323