Help Urgently Needed!

I would pick Chondrichthyes. How much of a Greek scholar is the setter of the question? I mean, there was not one single Greek word meaning "shark". There are various Greek words for different kinds of shark e.g. lamia, galeos, rhine.

The class Chondrichthyes (Greek, chondros = cartilage, ichthys = fish) contains the cartilaginous fishes, those that have a skeleton of cartilage rather than bone.

It contains two subclasses:

Elasmobranchii

Includes skates, rays (batoidea), and sharks (selachii).

No swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm.

Holocephali

Upper jaws are fused with their skulls; they have separate anal and urogenital openings; and they lack the many sharp and replaceable teeth of sharks, having instead a few large permanent grinding tooth plates.

Galocerdos are tiger sharks.

Many thanks contrex, very much appreciated.

The class Chondrichthyes is also known as Elasmobranchia. It includes the sharks, skates, and rays. They are termed "cartilliganeous fish."