Ischnothyreus browni Chickering, 1968: 83, figs. 11, 12 (male holotype plus one male and one female paratypes putatively from Costa Rica, probably mislabeled, in MCZ 66707, PBI_OON 49520, 49521; examined).

DIAGNOSIS: Males resemble those of I. aculeatus (Simon), from the Philippines, but can be distinguished by the distally enlarged, protruding projection on the male embolus (figs. 143, 149); females differ from those of I. aculeatus in having relatively short posterior genitalic ducts (figs. 159–161).

MALE (PBI_OON 35514, figs. 133–151): Total length 1.14. As in male of I. peltifer except as noted. Carapace pale orange, broadly oval in dorsal view. Sternal setae evenly scattered. Fangs without prominent basal process. Labium anterior margin not indented at middle. Dorsal scutum yellow, extremely weak, covering about half of abdomen length, between 1/4 and 1/2 of abdomen width, not fused to epigastric scutum. Postepigastric scutum yellow, covering about 1/3 of abdomen length. Spinneret scutum absent. Spinnerets not scanned. Leg spination: femora I, II p0-0-2; tibiae I, II v4-2-2; metatarsi I, II v2-2-0. Tarsal claws, tarsal organs not scanned; trichobothria not examined. Palp with proximal segments, cymbium, bulb all brown; tibial trichobothria not examined; bulb more than twice as long as cymbium, not bent before apex, with one protuberance on ventral side; embolus light, with distinctive dorsal process, process wider at tip than at origin.

FEMALE (PBI_OON 49521, figs. 152–161). Total length 1.36. As in female of I. peltifer except as noted. Carapace yellow, ovoid in dorsal view. Sternum yellow. Palpal femur with spiniform setae. Pedicel scutum not extending far dorsal of pedicel. Dorsal scutum, if present, with limits not detectable in this faded, possibly teneral specimen; epigastric scutum so weakly sclerotized that its limits are unclear. Postepigastric scutum very weakly sclerotized, apparently longer at middle than at sides. Leg spination: femora: I p0-1-2; II p0-0-2; tibiae I, II v4-2-2; metatarsi I, II v2-2-0. Tarsal claws, tarsal organs not scanned; trichobothria not examined. Postepigastric scutum probably with narrow transverse ridge at about half its length; squiggled posterior duct with three transverse portions.

MATERIAL EXAMINED: Philippines: Luzon: Laguna Prov.: 4 km SE Los Baños, Apr. 8, 1977, Berlese, forest litter (L. Watrous, AMNH PBI_OON 1966), 1♂; Malaboo Camp, Mount Makiling, 3.46 km SSW Los Baños, 14°08.220′N, 121°12.352′E. May 10, 2011, miniwinkler, forest litter, elev. 675 m (H. Wood et al., CAS 43645, PBI_OON 35514), 1♂; Mount Makiling, 4 km SE Los Baños, Apr. 9, 1977, Berlese, mixed hardwood litter (L. Watrous, AMNH PBI_ OON 1965), 1♂.

DISTRIBUTION: Known with certainty only from Luzon Island in the Philippines; as indicated above, we regard the Costa Rican type locality as spurious.