James T,
I had a look at your attachments. As you say it’s the same records. When I first looked at your query I thought it might be hard to narrow your family down but having found the marriage and baptism, I am pretty confident this must be your family/families. So that gives you a specific area that they lived, but it’s still quite a wide area. 20 square miles I would have thought.
Quite understand re finding the handwriting difficult and not being able to make out some of the surnames. We can help with that because we are fairly used to them. Ask if unsure.
One general thing to know about Mc & Mac prefixes is that originally it was written M’ as in M’Calister or M’Donnell. (And you can see that in those parish registers). Mc & Mac variations gradually followed later. Possibly easier for printers, not entirely sure why, though you’ll find plenty of newspapers with M’ too. Folk may tell you that Mac was Scottish and Mc was Irish, or alternatively it indicated whether you were protestant or catholic. All total nonsense. They just spelled things according to whim. Originally it was all just M’. You should also know that McConnell is a variation of McDonnell. Watch out for that too.
You can see where Layde RC parish is on this map. RC parishes were generally a bit bigger than the civil parishes, and in this case the RC parish covers Layde and Ardclinis civil parishes. (So when searching any civil records bear both parishes in mind, not just Layde).
https://www.johngrenham.com/browse/counties/rcmaps/antrimrc.php#maps/
Do you have any clues as to James & Mary’s parents names, perhaps from their death certificates? Also do you know their fathers occupations?
If they happened to be farmers and were alive around 1826/28 then they should be listed in the tithe applotment records. Here are the tithes for both Layd & Ardclinis. You’ll find both surnames in both parishes:
http://www.irishgenealogyhub.com/antrim/tithe-applotments/ardclinis-parish.php
http://www.irishgenealogyhub.com/antrim/tithe-applotments/layd-parish.php
I do recommend Brian Turner’s excellent book on the surnames as both yours get detailed investigation and comment. There’s about 20 pages on McDonnell. I have e-mailed you 2 sample pages to give you a flavour. The book may mention your specific families but even if not, it should give you a bit of background to their lives in the Glens of Antrim and how they came to settle there.
The McDonnells current chief in Ireland, descended from Sorley Boy McDonnell who arrived from Islay in the 1500s, is the Earl of Antrim who lives in Glenarm Castle very close to Layde. The grounds and tea room are open to the public. And they usually have Highland Games once a year. Bagpipes, caber tossing, traditional dancing and all that rather entertaining nonsense.
https://glenarmcastle.com/
If you want to learn more about your DNA, do get in touch with Martin McDowell. Participation in his DNA project is free and he’ll answer e-mail questions about it. He really understands the subject in a way that I don’t. And if you join the periodic Saturday Zoom sessions he’ll again talk you through your own DNA. There might be a fee for that, not sure. Details on the NIFHS site. (It’s the DNA interest group.)
https://www.nifhs.org/dna/
You don’t have to join NIFHS to participate in the DNA project or attend the workshops and courses. But if you do decide to join, the branch covering the Glens is the Causeway Coast & Glens Branch. (I am the Chair of that Branch). We have monthly talks which are streamed to members who can’t attend in person.