Pterostylis erecta located on Red Rock Nature Reserve

I have probably seen this species Pterostylis erecta before (I know Alan Stephenson has told me it occurs in certain localities I have visited previously) but this is the first time I have found it by myself and worked out that it is a different species from the commonly seen, and closely related, "Maroonhood"(Pterostylis pedunculata).

Unlike Pt. pedunculata this flower lacks a "fat bottom".
And its tip of the galea is gently pointing upwards
(hence the name "erecta").

Pterostylis erecta

Unlike the "Maroonhood" (Pt pedunculata)
this plant is dark brownish green
instead of really dark almost black on the front.

Pterostylis erecta

Pterostylis erecta

The lateral sepals (the little "arms" sticking up in the air)
are held close to the Galea (the hood).

Pterostylis erecta

 Note the cheeky little poking-out labellum tip.
(click on image to enlarge it).

Pterostylis erecta

The ever reliable Colin and Mischa Rowan, of RetiredAussies.com have a good page of photos of these plants photographed last year, at Nowra.
Have a look at their excellent images.
http://www.retiredaussies.com/ColinsHome%20Page/OrchidsNSW/Pterostylis/Pterostylis%20erecta%20NSW/Pterostylis%20erecta%20NSW.htm

Edit: 
I left in a bit of a hurry, earlier (rushed off to Trivia Night)
I gave you links, but it is better to see the two species on the one page.

Pterostylis pedunculata

 Note the dark reddish-brown (mahogany coloured) front.

Pterostylis pedunculata

Note the white back of the flower,.
and the contrasting mahogany-coloured front of the flower.
Also the "gap" where the lateral sepals arch forward,
before swinging back up to form the "points".

Pterostylis pedunculata

 This shows what I refer to the "fat bum" of this species.
It is noticeably broader than the narrower Pterostylis erecta.

Pterostylis pedunculata

When presented together like these, it is hard to imagine not being able to tell them apart.

But in the field, without the two species together (in other words, working off memory), it is not that easy. For the two species are very similar in form.
Worse, there is another species as well, which is regarded as being between these two.

Pterostylis oblonga - which I shall leave for another day.

Its all too hard (for me) let alone for you dear readers.