Fene. 248 



ORDER SELACHII. — Acondylacanthus, Agassizodus, Am- 

 acanthus, Anlliodus, Apedodus, Aspidodiis, Asteroptychius^ 

 Batacanthus, Bathycheilodus, Bythiacanthus, Oalopodus, Car- 

 charopsis, Cheirodus, Cholodus, Chomatodus, Cladodus, Cli- 

 maxodus, Cochliodus, Compsacanthus, Otenacauthus, Ctenop- 

 etalus, OtenoptychLiis, Cymatodus, Dactylodus, Deltodus, Des- 

 miodus, Diplodus, Drepanacanthus, Edestes, Erismacanthiis, 

 Fissodus, Gampsacanthus, Geisacanthus, Glymmatacanthus^ 

 Gyracanthus, Harpacodus, Helodus, Ilybacladodus, Lambdo- 

 diis, Lecracanthus, Leiodus, Leptophractus, Lisgodiis, Listra- 

 canthus, Machaeracanthus, Marracanthus, Mesodmodus, Ora- 

 canthus, Orodus, Orthacaiithus, Peltodus, Periplectrodus, Fe- 

 ripristis, Fetalodus, Petalorhynchus, Fetrodus, Fhoebodus> 

 Fhysonemus, Flatyodus, Fleuracanthus, Fnigeacanthus, Foecil- 

 odiis, Folyrhizodus, Fristicladodus, Fristodus, Fsammodus, Fse- 

 phodus, Ftyctodus, Sandalodus, Steuimatodus, Stenacanthus, 

 Tanaodus, Thrinacodus, Trigonodus, Venustodus, Xystracan- 

 tlius, Xystrodus. — Also the more recently formed genera : 



Chitonodus, Copodus, Deltodopsis, Deltoptychius, Ectosteora- 

 chis, Eimemacanthus, Janassa, Orthopleurodus, Falceobatis, 

 Ftyonodus, Rhadininichtliys, Stenopterodus, T^sneodus, Tomo- 

 dus, Vaticiaodus. 



Of this long list we owe most of our knowledge to Dr. New- 

 berry, State Geologist of Ohio, and his numerous figures in the 

 Paheontological Volumes of that Survey; much to St. John 

 and Worthen, of the Illinois survey ; much to Dr. Leidy 

 and Frof. Cope. Very few genera and species have been ac- 

 curately determined from Fennsylvania ; the numerous speci- 

 mens collected are still to be studied and distributed to their 

 places in the lists. 



The oldest itsh spine known was found in Ferry Co., Fa., by 

 Frof. Claypole, in the Clinton Iron Sajidstone^ with fragments 

 of scales and plates and small pellets (apparently cojprolites). 

 See Onchus clintoni (F2, xii, and Spec. 50a-7, four.)— f-F«. 



The next oldest he found in Ferry Co., spints and plates in 

 the Bloom-field sandstone at the top of the Salina. See Onchus 

 pennsylvanicus ; Palaeaspis americana ; Palaeaspis bi- 

 truncata. (F2, xii.) — Vg, 



The fossil fish beds of Fennsylvania, co- extensive with the 



