Melanocetus murrayi

Actinopterygii: The Actinopterygii, or ray-finned fishes, constitute a class or subclass of the bony fishes. The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii. In terms of numbers, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. (Wikipedia)

Triangular: The base of the ichthyolith is the widest part.

Curved: The overall shape of the ichthyolith curves in one direction.

Cavity Wide: The ichthyolith's cavity is distinctively wide (defined as more than four times as wide as the "walls" surrounding it at its midpoint; alternately phrased, the cavity takes up more than than two-thirds of the total width of the cross-section at its midpoint).