XXI 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.—Marein 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. Ribs 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 Chirocentridae, 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 Jch- 
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: (@) with praedentary (praesymphysial) bone, Sawroce- 
phalus, Saurodon, (b) without praedentary, 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 20 
