rhombus

neljäkäs puhekieltä Any of several flatfishes once considered part of the genus (taxlink). (defdate)
1638, (w), Some Yeares Travels, I:

the greedy Tuberon or Shark arm'd with a double row of venemous teeth pursues them, directed by a little Rhombus, Musculus or pilot-fish that scuds to and fro to bring intelligence ....