MALACOPTERYGII 561 



capable of being thrust forwards, when at rest folded over and 

 received into a depression on the upper surface of the head ; the 

 narial orifice is single, and preceded by a barbel ; the gill-openings 

 are narrow, restricted to the sides. The ventral fins are inserted 

 far back, the dorsal and anal are short. The air-bladder is very 

 large, and the intestine extremely long and much convoluted. 

 Vertebrae 26 + 8. 



Fam. 14. Saurodontidae. Margin of the upper jaw formed 

 by the praemaxillaries and the maxillaries, the latter the more 

 developed and firmly united to the former ; these bones, as well 

 as the mandible, with teeth implanted in deep sockets ; palate 

 toothless. Supraoccipital separating the small parietals ; oper- 

 cular bones well developed ; symplectic present, exposed. Basis 

 cranii double. Eibs sessile, very low down on the centra ; no 

 parapophyses ; neural arches not fused with the centra. Pectorals 

 inserted very low down ; postclavicle apparently absent. Caudal 

 fin deeply forked, without fused hypurals. 



This family, comprising several Cretaceous genera, may be 

 regarded as ancestral to the Cliirocentridae, with or near which it 

 has been placed by Cope and various later authors. The normal 

 position of the symplectic, however, entitles its members to rank 

 as a separate family, and the autogenous neural arch, as well as 

 the distinctness of the bones supporting the caudal fin, are also 

 indicative of a greater generalisation. The restoration of Ich- 

 thyodectes as given by Loomis, shows a general form similar to 

 an ordinary Herring, but it does not appear to be reliable. 



The members of the Saurodontidae have been referred to two 

 groups : (a) with praedentary (praesymphysial) bone, Sauroce- 

 phalus, Saurodon; (&) without praedeutary, Chirocentrites, Portheus, 

 Ichthyodectes, Spathodactylus, Cladocyclus. These Fishes are from 

 the Chalk of Europe and North America, and some among them 

 attain a very large size, perhaps not less than two metres in 

 length. 



Fam. 15. Chirocentridae. Margin of the upper jaw formed 

 by the praemaxillaries and the maxillaries, the latter the more 

 developed and firmly united to the former ; these bones, as well 

 as the mandible, with large teeth not implanted in true sockets ; 

 minute teeth on the palatines, pterygoids, and hyoid bones, 

 Supraoccipital in contact with the frontals, separating the small 

 parietals ; opercular bones well developed ; symplectic hidden 



VOL. vii 2 



