Were dolphin-like; they showed his back above
The element they lived in."
For 'his' we should read their or the.
"By the rebound of yours; a grief that suites
My very heart at root."
'Suites' is shoots (see on L. L. L. iv. 3). Some read smites.
"To one so meek, that my own servant should," etc.
The poet may have written weak.