Body: Body size derived from measurements in microns of four partially engorged specimens. Length, 400 to 562, average 497; width, 237 to 326, average 300. Color, pale orange. Double eyes present, though small, inconspicuous and well removed from the lateral margin of the scutum. Spiracles and tracheae absent. Anal opening slightly anterior to midpoint from coxa III to posterior margin, probably varying with the degree of engorgement. Gnathosoma: Cheliceral base and palpal femur punctate. Cheliceral blade with five minute ventral teeth and a tricuspid cap. Palpal femoral and genual setae with rather long side branches. Lateral palpal tibial seta simple. Dorsal and ventral palpal tibial setae with short barbs. Palpal claw apparently two pronged. Palpal tarsus with six feathered setae and a short spine. Galeal seta simple. Legs: All legs with six segments ending with two claws and a claw-like empodium. Coxal setae 2-2-2 (one specimen had three setae on one coxa I). With the following specialized setae: Leg I, 2 genualae, 1 microgenuala, 2 tibialae, 1 microtibiala, 1 spur, 1 subterminala, 1 pretarsala; leg II, 2 genualae, 1 microgenuala, 2 tibialae, 1 microtibiala, 1 spur, 1 pretarsala; leg III, 1 genuala, 1 tibiala. The description of S. tarsalis, J. and T., the genotype species, mentioned the considerable variation in degree of feathering on the leg The same condition was noted on the leg setae of S. biplumulosa. Scutum: Broadly rectangular, about three times as wide as long; anterior margin slightly convex mesally and posterior margin with a definite concavity. Scutal setae similar in diameter and quality. Sensillae simple. Scutal measurements (mean of four specimens): AW-99, PW-127, SB-41, ASB-47, PSB-22, AP-42, AM-86, AL-71, PL-93, SD-69, S-95. Setae: Approximately 60 to 63 dorsal setae and 68 to 77 ventral setae, irregular in arrangement and variable in form from plumose to barbate. The dorsal setae varied in length from 80 to 105, while the ventral setae varied from 32 to 88, the shorter, anterior setae being more plumose than the longer, posterior setae. There seemed to be no definite humeral setae. A single pair of sternal setae was located between coxae II and III. Type data: Holotype, taken from a shrew-mole, Urotrichus talpoides, Mt. Fuji, Yamanashi Prefecture, Japan, August 17, 1954; deposited in the United States National Museum, No. 2222. One paratype, same data as the holotype, deposited at the Medical Zoological Laboratory, Institute for Infectious Diseases, University of Tokyo. One paratype, same data as the holotype, deposited at the Rocky Mountain Laboratory, Hamilton, Montana. One paratype, same data as the holotype, retained by the author. All collections were made by personnel of the Preventive Medicine Unit, Third Marine Division.