The first dorsal fin and the ventrals are transformed into pointed formidable spines, and joined to firm bony plates of the endoskeleton.
The scales are very small, often very much reduced, and there are frequently no enlarged ventrals on the compressed belly, but Platurus has broad ventrals.
The gobies (Gobius) are small fishes readily recognized by their ventrals (the fins on the lower surface of the chest) being united into one fin, forming a suctorial disk, by which these fishes are enabled to attach themselves in every possible position to a rock or other firm substances.
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