The spore print is very BLACK
The gills dissolve themselves (deliquesce)
It was growing in a mix of grass and dung
Is it Coprinus, Panaeolus, Psilocybe, Conocybe or Bolbitius ??

Arora Says:
a) "Coprinus has gills that digest themselves and Panaeolus usually grows in dung or manure" (pg 341)
b) Panaeolus "do not deliquesce as in Coprinus" (pg 353)
c) Psilocybe and Conocybe are common in dung, but do not have black spores" (pg 353)
d) Bolbitius "is reminiscent of Coprinus (particularly in the striate cap and tendency of the gills to
liquefy somewhat), but it has rusty-brown to bright yellow -brown rather than black spores" (pg 473)

My conclusion this is Coprinus.
Do you agree?

Doug Bowman suggests it may be Coprinus Plictalis
Wikipedia says: Coprinus plicatilis is now Parasola plicatilis


Note: Trudell (pg 199) says that the spores of Parasola plicatilis
"are strongly lentil-shaped. 9.5-13 x 6-8 x 8.5-10.5"
Maybe it is just that it can not be seen from my pictures,
but as I see the spores they do not appear to be lentil-shaped.