Fig. 135.—Dorsal surface of Pterichthys, after Pander. d, Dorsal fin; c, pectoral member; 2–10, head-bucklers; 11–13, dorsal bucklers.
Fig. 136.—Ventral aspect of Pterichthys, after Pander. 15, mandible (?); 16–21, ventral bucklers.
Fig. 137.—Coccosteus, after Pander. A, Anal fin; D, Dorsal fin; C, Heterocercal tail; c, notochord; n, neurals; h, hæmals; 6–24, bucklers.
[See Ray Lankester, A. Monograph of the Fishes of the Old Red Sandstone of Britain. Part I. Cephalaspidæ. Lond. 1868 and 1870. 4to.]
SECOND SUB-ORDER—ACANTHODINI.
Extinct. Body oblong, compressed, covered with shagreen; skull not ossified; caudal heterocercal. Large spines, similar to those of Chondropterygians, in front of some of the median and paired fins. The spines are imbedded between the muscles, and not provided with a proximal joint.
Acanthodes, Chiracanthus, from Devonian and Carboniferous formations.