Ichthyodorulites, the strong, bony, defensive spines of fossil shark-like fishes. Except in one or two Carboniferous genera, in which they were attached to the pectoral fins, these spines were imbedded in the muscular tissue in front of the dorsal fins. They were formidable weapons, sometimes nearly a foot long, and furnished with recurved denticles, capable of inflicting a serious wound. Their variously - ribbed or tuberculate exposed surface is enamelled with ganoine. In some cases, as in the living Chimcsrci, they have a broadly expanded wing-like base imbedded in muscle. Many of them have not been with certainty correlated with particular skeletons; but in other cases they have been found in their natural position.