ORDER GANOIDEI. 98 1 



the dorsal and anal fins correspond in number with their supporting 

 interspinous bones ; the opercular bones are like those of the Tele- 

 ostei ; there is frequently a median jugular plate on the first pair of 

 branchiostegals ; the development of the vertebral column varies ; 

 the tail is of the masked heterocercal type ; and the scales are rhom- 

 boidal, or may be occasionally replaced by angular scutes. This 



Fig. 920.— Platysomus gihbosus ; from the Middle Permian of Germany. Reduced. 

 The pelvic fin is not shown. 



suborder is represented at the present day by the somewhat aber- 

 rant Lefiidosteidce, and also by a large number of Mesozoic forms 

 ranging from the Trias upwards. As already mentioned, the exter- 

 nal resemblance of the Dapeditdce and Pycnodontidcz to the Platy- 

 so??iid<z is not regarded by Dr Traquair as indicative of real affinity. 

 Family Dapediid^. — In this family, which by some writers is 

 subdivided and known as the Sauridce and Stylodontidee, the body 

 is either fusiform or ovate ; the opercular bones present certain 



g 921. — Semioiiotus Kapjft; from the Keuper of Wiirtemberg. (After Fraas.) 



characteristic features ; the upper lobe of the body-axis of the tail, 

 and usually the anterior borders of the other fins, have well-devel- 

 oped fulcra ; the vomer and jaws carry several rows of small teeth, 

 of which the outermost are curved and resemble claws (griffehahne) ; 

 and the ossification of the vertebral column is imperfect. Among 

 the genera with fusiform bodies, one of the best known is Semioiiotus 



