Classification of the Order Iniomi. 131 



Family 2. Omosudidse. 



The genus Omosudis, Guuther, agrees with the Scopel- 

 arcliidae in its moderately elongate form and short dorsal fin 

 but it has the head, mouth, and teeth of the Alepidosauridae. 

 It differs from both in the pectoral arch, for the cleithrum is 

 not expanded and the postcleithra are long and slender and 

 reach the ventral profile. 



Family 3. Alepidosauridae. 



Body very long, strongly compressed, naked. Snout pro- 

 duced, pointed ; maxillary with a large triangular laminar 

 expansion anteriorly; no supramaxillary ; teeth compressed ; 

 lower jaw with one or a pair of canines on each side. Skull 

 triangular in form when seen from above, gradually increasing 

 in width backwards ; interorbital region flat, moderately 

 broad ; parietals separated by the supraoccipital ; posterior 



Fior. 6. 



AlejAdosaurus ferox ; lateral view of skeleton of head and pectoral arch. 

 Lettering as in figures 2 and 5. 



temporal fossaj not roofed ; lateral ethmoids meeting in the 

 middle line ; suborbitals not ossified. Postcleithra laminar ; 

 cleithrum much expanded, triangular or triradiate in form. 

 51 vertebrge ; centra long, without transverse processes ; ribs 

 slender, sessile. Dorsal fin very long, of simple non-articu- 

 lated rays. 



The skeletal characters given are those of an example of 

 Alepidosaurus ferox. 



The Cretaceous Apateodus is known from the skull, 

 jaws, and teeth, which seem to be very similar to those of 

 Alepidosaurus and Omosudis. 



