Basidiomata gregarious, flabelliform, spathulate, ligulate when young to subdimidiate when mature, convex to subconchate, sessile to pendent (i.e. not everted-curled like L. cochleatus). Pileus 7-32 mm broad, up to 24 mm deep, subundulate to delicately radially rivulose, "Rood's brown" to "pecan brown" (6C5-6135), russet to (where poorly dried) brown-black, "orange buff' to "capucine buff' (5A5-6) or duller (5B5-7), with spots of "buckthorn brown" (5136), surface smooth outward, minutely pubescent to minutely micaceous at disc, more hirsute or hoary at stipe attachment; hoary ornamentation yellow, drying pallid gray; margin translucent-striate, decurved, fimbriate to crenulate but not striate, darker than pileus, as though hygrophanous (5B5); flesh thin (less than 1 mm thick). Lamellae adnate, subdecurrent, subdistant, up to 3.5 mm deep, in at least three ranks, "pale cinnamon pink" (5A2-3) to "cinnamon buff' when fresh, drying to "tilleul buff'.to (poorly dried) dark brown (5135, 6C4); margin coarsely digitate-serrate, reported as minutely white. Stipe lateral to absent, 2-10 X 2-4 mm, prominent, reduced to a knot or absent, more or less equal (when present), irregular in cross-section (i.e. not terete, fluted by lamellar ridges), near "buckthorn brown" (5137), dark brown, "drab," to "light drab," strigose, plushy to covered with hyphal spikes. Odor very weak, typical; taste very slowly weakly acrid, mildly anesthetic to tip of tongue.

Pileipellis a repent, radial, coherent layer of generative hyphae involved in mucus; hyphae 2.0-7.0 µm diam, hyaline to yellowish brown (BF, KOH), thin-walled, clamped; mucus epi- and interhyphal, discharged in globules in squash mounts (PhC, KOH), amorphous, not granular. Suprapellis outward undeveloped but lanceolate pileicystidia emergent from generative hyphae; pileicystidia (Fig. 24) 55-92 X 6.7-13.0 µm, ranging from elongate-ellipsoid with bluntly rounded apex to fusoid with prolonged beak, to fusiform-lanceolate, gradually tapered to bluntly lanceolate tip, hyaline, sometimes biaxial, thin-walled, inamyloid; inward pileicystidia gloeoplerous, 150-340 X 6.5-17.0 µm, narrowly vermiform to nematoform, tapering to narrow apex, undulate to irregularly swollen, thick-walled (wall up to 1.8 µm thick), yellow-refringent (PhC, KOH), inamyloid; contents glassy to finely coscinoidal; pileileptocystidia numerous, 2.0-3.0 µm diam, hyaline, filamentous, rounded at apex, twisted to delicately undulate, emergent up to 45 µm. Subpellis of outer pileus dimitic: 1) generative hyphae 3.0-6.0 µm diam, hyaline, thin-walled, clamped; and 2) gloeoplerous hyphae abundant, sinuous, yellow-refringent (PhC, KOH); contents cosdinoidal; subpellis of inner pileus dimitic: 1) generative hyphae undulate, thick-walled (wall up to 0.7 µm thick), hyaline, clamped; and 2) gloeoplerous hyphae occasional, as in outer subpellis.

Pileus trama interwoven, dimitic: 1) generative hyphae 2.0-7.5 µm diam, hyaline, thick-walled (wall up to 1.3 µm thick, commonly occluding cell lumen), glassy-refringent over short lengths, long-celled, branched, inamyloid to weakly amyloid (pale blue-gray), conspicuously and frequently clamped, occasionally ornamented with minute warts on exterior surface and then appearing minutely banded; and 2) gloeoplerous hyphae common (not abundant) near surface, less so inward, 3.5-7.0(-14.0) µm diam, yellow-refringent (PhC, KOH), thin-walled, emergent up to 15 µm; and 4) leptocystidia (Fig. 25c) filamentous, 1.8-3.0 µm diam, yellow-refringent (PhC, KOH), emergent up to 15 µm; contents coscinoidal.

Basidiospores (Fig. 25d) 4.0-5.7 X (3.5-)4.0-4.5 µm (E = 1.08-1.33; Em = 1.20; Lm = 4.85 gym), ovate to broadly ovate to subglobose, thin-walled, weakly to moderately amyloid; ornamentation of densely scattered, strongly amyloid prickles barely visible at 1500X;contents homogeneous to uniguttulate.

ETYMOLOGY: Referring to the chlamydospores on the margin of pileus and the white edge of the lamellae.

The production of chlamydospores on the margin of the cap is a very distinctive character in Lentinellus marginatus. L. cochleatus seems to be the only other species reported to produce chlamydospores but they are described as being either on the stipe (Miller & Stewart 1971) or formed interstitially beneath the pileipellis (Breitenbach & Kranzlin 1991). Also, the basidiomata of L. cochleatus are different in form, with well developed, long stipes in tightly fused caespitose clusters (Miller & Stewart 1971).

Shown to be a synonym of Lentinellus ursinus by Pegler 1983.

Berkeley's (1855) description is "Subimbricated. Pileus 1 inch or more long and broad, thin, flabelliform, suborbicular or reniform, bay brown, clothed behind with short velvety olive down. Stem obsolete. Gills same colour as the pileus, narrow, decurrent behind; edge thin, lacerated. Closely resembling L. castoreus, of which I have an authentic specimen, but differing in size and narrow gills."
The type material (New Zealand: Colenso, Herb. Phillips, ex Herb. Berkeley, K) consists of 4 basidiomata up to 26 x 17 mm diam. Their characters all confirm Pegler's identification of the species as yet another synonym of L. ursinus.