86 



PISCES 



CLASS I 



f 



Frontal profile steep. Vomero-palatine with five rows of rounded, bean-shaped 

 teeth, of which the convex crown has a rugose border and mammillated apex ; 

 the middle row larger than the lateral rows. Splenial with four rows of 

 similar teeth ; dentary with three stout prehensile teeth. Caudal fin deeply 

 forked, symmetrical. Common in the Upper Jurassic (Lithographie Stone) of 

 Solenhofen, Eichstädt, Kelheim, Cerin (Ain) ; also in the Kimmeridgian of 

 England, France, and Switzerland, in the Portlandian and Neocomian of 



^^P^Ä 



Fig. 155. 



Gyrodus tifanius, Wagn. Scale, inner (A) 

 and outer {B) aspects, nat. size. Kellieini. 



Fig. 154. 



Head of Gyrodus macropMhalmns, Ag. Upper Jurassic 

 (Lithographie Stone) ; Kellieini, Bav:iria. c, Slime canals ; 

 d, Clavicle ; eth, Ethmoid ; fr, Frontal ; md^ Mandible ; j/i.>, 

 Maxilla ; 0, Orbit ; op, Preoperculum ; pa, Parietal ; pfr, 

 Post-frontal; ptiu^ Premaxilla ; pt, Post - temporal s ; sc, 

 Sclerotic ring ; sei, Operculuni ; sq, Squamosal. 



France and Switzerland, and the Tithonian 

 of Sicily. Some species from the Litho- 

 graphie Stone {G. tifanius, Wagner) attain 

 a length and depth of 1 m. 



Microdon, Ag. (Figs. 158, 159). 

 Hinder half of trunk with very thin 

 scales, which are often wanting. Vomero-palatine slender, with five rows of 

 quadrate, smooth, and fiattened teeth ; between the large teeth of the middle 

 row the smaller teeth of the two inner lateral rows are alternately pressed 

 inwards. Splenial with one row of large, obliquely quadrate, smooth teeth, 

 which is fianked inside by one, outside by two rows of smaller teeth. Caudal 

 fin slightly forked, symmetrical. Common in the Upper Jurassic (Lithographie 



Fig. 156. 

 Gyrodus titanius, 

 Wagn. Palatal plate 

 Avith teeth, nat. size. 

 Kelheim. 



FiG. ir 



Gyrodus titanius, 

 Wagn. Right splenial 

 with four rows of 

 teeth, nat. size. Upper 

 Jura ; Kelheim. 



