38 



PISCES 



to the head, and the pelvic pair are separated from them by an interspace ; 



the tail is slender, and mouth narrow. There are no fin spines. 



Petalodus, Owen {Chomatodus, Ag. in part ; Sicarms, Leidy ; Antliodus, 

 Newb. ; Lisgodus, St. John and Worthen), (Fig. 

 75). Teeth much antero- posteriorly compressed 

 and transversely elongated. Crown leaf- shaped, 

 with cutting edge and sharp basal margin with 

 enamel folds ; root long and comparatively slender, 

 truncated below. P. acuminatus, Ag. sp., and other 

 species from the Carboniferous Limestone of Eng- 

 land, Scotland, Ireland, Belgium, Russia, and 

 North America. Rare in the Coal Measures of 

 North America. 



Petalorhyiichus, Newb. and Worth. Dentition 

 consisting of six transverse rows of three acumi- 



Carboni- 



SmT^.^^""^'"'''''™"°''^'''"'' ferous Limestone; Europe and North America. 



Janassa, Miinster (Didaea, Byzenos, Miinster : 



Climaxodus, M'Coy ; Peltodus, Newb. ; Tanaodus, St. John and Worthen), (Fig. 



76). Dentition consisting of narrow and elongated teeth with a reflexed 



punctate crown, which are arranged in five to seven longitudinal, and seven 



transverse rows, three on either side of the symphysial series. The oral 



Fig. 75. 



Petalodus alleghaniensis, Leidy, 

 Tooth in front view (A) and trans- , ,,. , ,^ ■,■• t • i ^ j_ 



verse section (£), 1/2 Mt- size. Coal nate cuttmg teeth With undivided root 



Janassa hUnminosa, Schloth. sp. Kupterscliiefer ; Glilcksbrunn, Tluiringia. A, Upper and lower dentition. 

 B, Cross-section. (', Tooth from iii front, and D, from beliind. E, Dermal tubercles, enlarged. 



cutting margin is formed entirely by the anterior face of the crown, which 

 is bent backwards sharply and overlaps the next older tooth in front, 

 which serves as a support. The long, tapering root of each tooth is 

 much compressed antero-posteriorly, slightly arched, transversely ridged on 

 the convex anterior face, smooth on the concave hinder face. Skin covered 

 with oval or quadrate, smooth, shagreen granules. /. hitumhwsa, Schloth. sp. 

 (Fig. 76), represented by important specimens from the Kupferschiefer of 

 Hesse and Thuringia, also from the Marl Slate of Durham. Detached teeth 



