The Roman Map of Britain Lambay

Regaina (R&C 277) next

Both Rathlin Island and Lambay Island  were once known as Rechriu,  Rech-eriu 'standing before Erin' according to McClure.

Lambay seems the more likely for its position between Anglesey and Man in the Ravenna Cosmography. The traditional choice is Rathlin. Rathlin should be the  Rikina Ricina (Ptolemy II 2 10), as it is one of the Ebudae listed by Ptolemy.