The Light Blues hopes of staying in the top flight look grim following this defeat as they are now ten points off the relegation places.
The home side trailed 19-3 at half time with Conan Doyle kicking a penalty and he converted a try from Ronan O'Mahony eight minutes from time.
Dolphin's yo-yo season continued when they got back to winning ways with a 25-18 home win over Ballynahinch.
Tries from John Quill, Cian Bohane and James Kiernan gave Dolphin a 19-8 interval lead. Rory Scannell converted two of the tries. Scannell added two penalties in the second half.
Young Munster were defeated 46-28 by leaders Clontarf at Castle Avenue.
In an evenly contested first half two penalties and a drop goal from Willie Staunton saw the Limerick side trail13-9 at half time. The home side ran in six tries in the second half and Munster's reply were two tries from Derry O'Connor and one by Tom Goggin with Staunton converting two of them.
Cork Constitution were defeated 23-17 away to UCD. It was 3-3 at half time with Johnny Holland kicking a penalty for the Temple Hill side. Cathal O'Flaherty and Luke Duffy scored second half tries for the visitors and Holland converted both.
In Division 1B U.L. Bohemian bounced back after last week's defeat with a 29-13 away win over Dungannon. Kevin O'Byrne, Jack O'Donoghue, Mossy Lawler and Shane Boyle scored tries for "The Robins" and Robert Bourke kicked three conversions and a penalty.
Shannon eased their relegation worries with a 13-9 win over Belfast Harlequins at Coonagh. An Injury time try by Luke O'Dea decided this contest. Rob Guerin scored Shannon's first half try as they trailed 9-5 at the break. Gearoid Lyons kicked a second half penalty.
In Division 2A Leaders City of Derry travelled to Bruff and defeated the home side 29-19 a result that leaves the Co. Limerick side propping up the table.
U.C.C. lost valuable ground when they were defeated by NUIM Barnhall 17-14 at Maynooth in the Kildare side's first ever colours game. Sean Og Murphy and Cian McGovern scored tries for U.C.C. and Murphy converted both.
Cashel defeated Rainey Old Boys 19-15 at Hatrick Park.
Old Crescent eased their relegation worries with a 19-8 home win over Seapoint.
A magnificent second half comeback by Highfield saw them win their first game of the season to come from 16-6 down at half time to defeat Old Wesley 28-19. Sean Quaid, Jason Carton and Dave O'Hea all scored tries for the 'Field and Ian O'Donoghue added three penalties and two conversions.
Nenagh Ormond remain top of Division 2B after top of the table clash at Skerries which they won 18-17.
Thomond kept up their challenge with 27-14 away win over Boyne.
Midleton lost away to struggling Sligo 16-11.
Richmond eased their relegation worries with a 25-19 home win over DLSP and a last minute converted try denied
Sunday's Well the spoils at Spollanstown when they were held to a 22-22 draw by Tullamore.
Ulster Bank League Division 1A: Clontarf 46, Young Munster 28;
Dolphin 25, Ballynahinch 18;
Garryowen 10, Lansdowne 35;
St. Mary's College 24, Old Belvedere 27;
U.C.D. 23, Cork Constitution 17;
Division 1B: Blackrock College 22, Buccaneers 41;
Dublin University 22, Malone 20;
Dungannon 13, U.L. Bohemian 29;
Galway Corinthians 10, Terenure College 57;
Shannon 13, Belfast Harlequins 9;
Division 2A: Banbridge v Galwegians postponed
Bective Rangers 15, Queens University 32;
Bruff 19, City of Derry 29;
Highfield 28, Old Wesley 19;
N.U.I.M. Barnhall 17, U.C.C. 14;
Naas 14, Ballymena 18;
Old Crescent 19, Seapoint 8;
Rainey Old Boys 15, Cashel 19;
Division 2B: Boyne 14, Thomond 27;
Instonians 36, Ards 6;
Navan 32, City of Armagh 24;
Richmond 25, D.L.S.P. 19;
Skerries 17, Nenagh Ormond 18;
Sligo 16, Midleton 11;
Suttonians 10, Greystones 21;
Tullamore 22, Sunday's Well 22;