COCCOSTEUS, k5k-kiss't(t-tis (Neo-Lat.. from Gk. K6KKOT, kokkos. berry-I-oar/or, ostcon. bone). A genus of heavily armored fishes. of the order Arthrodira, fossil remains of which arc found in the Devonian rocks of Europe and North America, The head and the forward part of the trunk were covered with strong, bony plates, and the plates of these two regions articulated by a binge-joint that admitted of free movement of the head upon the trunk. The skull had large orbits. placed well forward, and in the middle of the frontal surface was a pit that indicated the position of the pineal body. The jaws were strong. and the mandibles or lower jaws were furnished with conical teeth. The trunk of Coe costeus was shark-like in form. and was provided with a single dorsal fin, an anal fin. and a pair of rudimentary pelvic fins. It was probably covered by a soft skin that readily decomposed after the death of the animal, and that hence escaped fossilization. The vertebral column shows
an interesting progressive stage in the evolution from the cartilaginous backbone of the earlier fish to the completely calcified skeleton of the later genera. The neural arches and the spiny processes of the vertebra have alone become cal eified. so that in well-preserved specimens they appear as two rows of bony processes, with an intervening empty canal that represents the car tilaginous centra or 'bodies' of the vertebral elements. the species of the Coccosteus are small, none of them having been found with a length greater than 20 inches. The best-known sTecies and the type of the genus is Coeeosteus decipiens. which is common in the Old fled :sandstone of the Scottish Devonian. A few specimens, though none so perfect as the Scot tish, have been found in the North American De vonian. See Fisn; Dtexot: LUNG- Fisn.