Hi, found some bits that may help.
Marriage:
19 October 1869
Long Tower,co Derry
Richard Gallagher & Ellen Clarke
witnesses:William McCausland & Rose Doherty
married by Rev William McLaughlin
Births for Richard 1840-1860:
Richard Jones Gallagher
bap:13 June 1847
Killinchy,co Down
parents:John Gallagher & Mary
Richard Gallogher
bap:24 March 1856
St Patricks,Belfast,co Antrim
parents:Charles Gallogher & Ellen Mooney
Richard Edward Gallaher
bap:17 November 1859
Long Tower,co Derry
parents:Charles Gallagher & Sara Devlin
* I think on this one either priest or transcriber has the year wrong
births for Ellen:
co Derry;
Ellen Clarke
born 30 May 1848 Portrush
parents:Robert Clarke & Martha O'Brien
Ellen Clarke
bap:13 June 1850 Cumber Upper
parents:John Clarke & Margaret Crocket
Ellen Clarke
born 13 Sept 1847 Kilrea
parents:Joseph Clarke & Ellen Kyle
Ellen Clarke
bap:31 March 1853 Cumber Lower
parents:William Clarke & (mom not listed)
Baptisms for some children of Richard & Ellen:
Francis
bap:18 February 1870 Long Tower,co Derry
sponsor:Susan Mullan
Mary
bap:22 December 1872 Long Tower,co Derry
sponsors: Patrick Clarke & Catherine Clarke
Richard
bap:9 January 1875 St Eugene's,Derry
sponsors:Francis Mullan & Marian McGowan
Susanna
bap:25 November 1879 St Eugene's,Derry
sponsors:Susan Logue & Hugh Gallagher
Ellen
bap:29 January 1882 St Eugene's,Derry
sponsors:James McGinnis & Ellen Gallagher
John
bap:4 March 1887 St Eugene's,Derry
sponsors:Bernard McDaid & Maggie Clarke
*(beneath this is note that John married Isabella McSweeney at Long Tower church,Derry on 28 October 1915)
Patrick
bap:29 September 1889
sponsors:Charles Gallagher & Bridget Clarke
Hope this helps,Kim