Big Monday Crossword 21/08

[bubbles0809]

1d)Verse of poetry comprising four lines QUATRAIN?????
16d)Branch of dentistry concerned with the soft tissues surronding teeth? (12letters)??
30d) Herbivorous sea mammel of the genus Trichechus, found in warm Atlantic waters and coastal rivers of Africa and America????? (7 letters)
15a)Situation in which no furthur progress is possible (7 letters)???
11a) Subdivision of a calvary unit,usually commanded by a captain TROOP?????? THANKS : ) : ) : ) : )

[squarebear]

1d quatrain
16d periodontics
30d manatee
15a impasse
11a troop

[BigMac]

bubbles, just a note of help. Most people on the site use the '?' symbol to denote a missing letter, so all your '????s' are a little confusing.

The best form is 'Clue (x)' (where 'x' is the number of letters) followed by any letters you have. So, as an example:

1d Verse containing four lines (8) ??A?RA?N