The Cornwall HER website has this to say:-
Carn-men-ellas entrance grave was first sketched by Borlase (b1) who later excavated the site and discovered that it had been disturbed (h1, b2). No finds were recorded. Sketched by Henderson (h2, b3) and later surveyed by the OS (h1) and resurveyed by CAU/National Trust (h4, b7, b8), with a further field visit by the OS in 1985 (h5). The site stands on cliff land and is covered by fescue-thrift grass. Overall diameter of the mound is 91m which is ringed by a partially extant kerb of just 5.3m to 5.7m in diameter (b7). There are extant remains of a central stone cist. Although damaged, remains are essentially intact. Herring (b7) suggests that this site may be an entrance grave rather than a kerbed cairn with cist (b5) and therefore does not group it with cairns in the vicinity. The site should be scheduled.
The site is believed to be a Scillonian Entrance Grave rather than a simpler Cairn & Cist but you decide!
Something is not right. This message is just to keep things from messing up down the road