BRIEF DESCRIPTION: The following is largely based on the original description (1941).

The cap of Amanita umbrinella is around 75 mm wide, hemispheric at first, convex becoming planar, center becoming depressed, viscid to dry with a lightly striate margin that is sometimes not apparent at first.  The cap can range from grayish brown to saturated olive-chestnut, bistre, very dark umber, chocolate, drab hair brown, or olivaceous-black.  The volval remnants on the cap are grayish-white warts sparsely distributed or, occasionally, as a single patch (white at first and graying).

Gills are rather crowded, very close to the stem or even attached to it, white or very pale cream colored, often becoming pinkish, and, in dried material, sometimes becoming purplish.  The short gills are numerous, squarely truncate, and sometimes seeming to reflect a purplish tint.

The stem is about 75 ×15 mm, narrowing upward, with a fibrillose surface.  The stem may be more pallid than the cap, but the basal part will often be distinctly gray or gray-brown.  The bulb is 25 mm wide and is pronounced or marginate or neither.  When the bulb is not clearly defined, the stipe base is sometimes pointed.  On the bulb's border, there is a limbate volva which is submembranous to friable and often falling away.  The ring is membranous, ample, and persistent.  It's white to somewhat sordid and finely striate above.

The spores measure approximately 11.5 - 13 × 9 - 11.5 µm.  Presence or absence of clamps on bases of basidia not known.  Its author reports that spores were not found in the original material of A. bambra Grgur.  Wood (1997) presents a confusing picture on basidial clamps in this species indicating that they can be present and not rare in some cases as well as absent in others.  Moreover, he applies the name umbrinella to a taxon with pale pigments.  Considering the phenetic similarity of the present species with taxa bearing plentiful clamps, I'm inclined A. umbrinella will be found to bear clamps on its basidia.  Very often one can get a small sample of spore size and shape from the illustrations of Gilbert (1941).  In the case of A. umbrinella, there is so much variation in the spore shapes drawn for the species that we have chosen only to use the information from the holotype and one paratype (called syntype by Gilbert).  Among these only four were presented in lateral view; and (as is our usual microscopic procedure) these were the only spores on which we took data.  The resulting measurements yield 11.5 -14 × 8.8 - 9.8 µm and are ellipsoid.

This species is originally described from the state of South Australia where it was found in sandy soil. Reid (1980) cites reports of its presence in the states of Victoria and West Australia. The authors indicated no nearby tree species.  Amanita umbrinella is also reported from New South Wales with Eucalyptus.

The dark shades of brown and gray in the cap, the submembranous grayish limb of the volva, large spore size, a ring that sometimes is lost, all strongly suggest a group of species probably related to (or even synonymous with) Amanita merxmuelleri Bresinsky & Garrido described from Nothofagus forests in Argentina and Chile.  Further examination of the potential relationship could be very helpful in understanding the dispersal of formerly Gondwanan mycota.  Amanita murinoflammeum Tulloss, A. M. Young & A. E. Wood was originally described as belonging to section Vaginatae; however, further study shows it to be somewhat similar to A. umbrinella in macromorphology. Photographs or careful drawings of sections of buttons of this and possibly related taxa will be valuable in understanding their morphological taxonomy. -- R. E. Tulloss and L. Possiel