Page:The American Cyclopædia (1879) Volume VII.djvu/627

 GANOIDS 615 interesting genera is dipterm, in which D. macrolepidotus of the old red sandstone re- sembles a fish carved in ivory, crusted with Dipterus macrolepidotus. enamel, and thickly dotted with minute punc- turings; with circular scales, thickly enam- elled fin rays, strong angular pectorals, scale- Osteolepis. protected ventrals like the hind fins of the ichthyosaurus, and a long dorsal and anal, the former consisting of two portions. Osteole- pis, also British Devonian, has two anals alternating with two dorsals, large and rounded pectorals, small ventrals, large mouth, and scales of moderate size. Among the genera most numerous in the coal measures are palceoniscus, a small, handsome, and well proportioned fish, with moderate-sized no ventrals, large pectorals, and very wide mouth, in proportions resembling the conger eel or ling. Among those most numerous in the Jurassic age are tetragonolepis, with a broad flattened body, rapidly decreasing to the tail, rounded head, moderate fins, and pointed teeth about 20 species in Europe ; lepidotus, with body shaped like a carp^, large rhomboidal scales, and caudal fin almost square about 30 species; and pholidophorus, resembling the herring, but with rhomboidal scales, homocer- cal or equal-lobed tail, and small teeth more than 30 species. In the family of cephalaspids, which contains the extreme acanth forms for a long time not recognized as fishes by palaeon- tologists, the body and head are covered with a few non-imbricated plates or shields; the heterocercal tail, covered with imbricated scales, has no true caudal fin ; and in place of pectorals are two long bony appendages or sti- Palaeoniscus. fins and scales, a single dorsal opposite the space between the ventrals and anal, and all with small rays at their margins about 30 species in North America and northern and central Europe; eurynotus, a flattened and breain- Tetragonolepis. shaped species, with large dorsal, ventrals, pec- torals, and head ; and anthodes,wt}i lengthened body, very small scales, dorsal opposite anal, Pterichthys Mffleri. lets ; the dorsal cord like that of the sturgeons ; they belong to the old red sandstone formation, and were short-lived in comparison with some other ganoids. The genus pterichthys (winged fish), discovered by Hugh Miller in the Oro- marty sandstone, first appears at the base of the old red sandstone, and disappears with its up- per beds; one of the best known species, P. Millet 'i, is 8 ft. long ; it is as strange a form among fishes as the plesiosaurus and pterodac- tyl among reptiles; in his work on "Fossil Fishes," Prof. Agassiz says: "It is impossible to find anything more eccentric in the whole creation than this genus." Hugh Miller de- scribes it, when seen from the under surface, as resembling "the human figure, with the arms expanded as in the act of swimming, and the legs transformed, as in the ordinary figures of the mermaid, into a tapering tail." There is no separation between the head and trunk, and the whole animal is in a complete armor of solid bone ; the strong helmet of the head is perforated in front by two circular holes for the eyes, the body above and below protected by a curiously plated cuirass, and the tail sheath- ed in a flexible mail of bony scales ; the plate- covered arms are articulated by a complicated joint to the lower part of the head ; the flat