A taxonomie investigation of the interstitial mites collected from Nobska Beach, Woods Hole, Massachusetts, revealed that representatives of the suborders Mesostigmata, Trombidiformes, and Sarcoptiformes are present. Members of the family Rhodacaridae (Mesostigmata) were the most common in all samples, the Halacaridae (Trombidiformes) somewhat less. Acaridiae and Oribatei (Sarcoptiformes) were very rare. Detailed study of the family Rhodacaridae revealed the presence of 5 genera of which 4 have been previously described, but are reported for the first time from this area. The new genus and species Psammonsella nobskae, is characterized by the presence of 5 pairs of long simple but unequal setae arranged in a cresentic pattern at both sides of the anterior margin of the notocephale, and by fusion of the ventri-anal plates with the petritremal plates, in both sexes