36 PISCES CLASS I 



of.C. latus, Leidy, from Keokuk Limestone of Mississippi Valley, the largest 

 known species, originally described as Helodus coxanus, Newb. Lower Carboni- 

 ferous ; Ireland, England, Belgium, and North America, 



Streblodus, Ag. As Cochliodus, but hinder tooth with two to three broad, 

 oblique, transverse folds. S. oblongus, Ag., and *S^. colei, Davis, from Carboni- 

 ferous Limestone, Armagh. Other species from England and North America. 



Sandalodus, Newberry and Worthen (Trigonodus, Faticinodus, N. and W. ; 

 Orthopleurodus, St. John and Worthen). Supposed upper teeth triangulär, 

 thick, slightly inrolled. Supposed lower teeth more strongly inrolled ; the 

 hinder one subtriangular or twisted and elongate, with one to two diagonal 

 ridges, and anteriorly coiled in a distinct whorl ; the anterior one short, 

 truncated in front, strongly inrolled. Carboniferous ; Ireland, England, 

 Belgium, and North America. 



Deltoptijchius, Ag. ; Chitonodus, St. John and Worthen ; Poecilodus, Ag. ; 

 Deltodus, Ag. (Taeniodus, St. J. and W.) ; Xystrodus, Ag. Carboniferous Lime- 

 stone ; Europe and North America. 



Psephodus, Ag.^ (Fig. 72). Large rhombic or rhomboidal teeth, convex 

 and gently arched, with crenulated border. With these large teeth are 



% 



Fig. 72. 



Psephodus niagmis, Ag. A, Three teeth in connected series, nat. size, from the Carboniferous Limestone 

 of Armagh (after Davis). B, Associated upper teeth from remains of head found in Calciferous öandstones, 

 Bast Kilbride, Lanarkshire. b, Large tooth somewhat broken ; c, Small tooth identical with Helodus rudis, 

 M'Coy; d, ölender teeth identical with Helodus planus, Ag. ; e, Helodont teeth; /, g, Teeth identical with 

 Lophodus didymus and L. Imvissimus, Ag. sp. (after Traquair).- 



sometimes associated more numerous transversely elongated small teeth, of 

 which isolated examples have been described under the names of Helodus, 

 Lophodus, and Aspidodus. Carboniferous Limestone ; Europe, India, and North 

 America. 



PleuToplax, Sm. Woodw. {Pleurodüs, Hancock and Atthey, non Wood, nee 

 Harlan). Teeth with feeble antero- posterior ridges, and the antero- and 

 postero- lateral borders indented between these ridges. These teeth some- 

 times associated with others of the Helodus-type. At least one dorsal fin, with 

 an unornamented spine. P. rankinei, H. and A., from English Coal Measures. 

 Other species from Upper and Lower Carboniferous of Europe and North 

 America. 



Menaspis, Ewald, emend. Jaekel ^ (Bichelodus, Giebel ; Chalcodus, Zittel), 



^ Traquair, R. H., Trans. Geol. See, Glasgow, vol. VII. 1885, p. 392. 



2 Jaekel, 0., Ueber Menaspis (Sitzungsb. naturf. Freunde, Berlin, 1891, p. 115). — Reis, 0., lieber 

 die Koptstacheln von Menaspis armata, Muuich, 1891. 



