Two new species of the genus Provanna, which is now known to be a hydrothermal vent associated gastropod genus, were collected from the "snail pit" in Mariana Back-Arc Basin by the DSRV Alvin in 1987. They are named P. nassariaeformis n. sp. and P. marianaensis n. sp., and both are associated with a mass aggregation of the hairy snail Alviniconcha hessleri Okutani & Ohta, 1987.