XXI OSTARIOPHYSI Usa 
from the Upper Cretaceous of Westphalia and Mount Lebanon, 
has also been included in this family, but the precise shape and 
character of the scales have not yet been ascertained. 
Fam. 21. Cromeriidae.—Margin of the upper jaw formed by 
the praemaxillaries and the maxillaries. Supraoccipital large 
and widely separating the very small parietals; opercular bones 
well developed; symplectic absent. Basis cranii simple. Mouth 
small and toothless, inferior; gill-opening narrow. Three 
branchiostegal rays. Body naked. Praecaudal vertebrae with 
parapophyses; ribs and epipleurals slender. No postclavicle. 
Pectoral fin inserted low down, folding like the ventrals. 
A single genus, Cromeria, recently discovered in the White 
Nile. In its elongate, naked body and the posterior position of 
the dorsal fin, it resembles the Galaxiidae, to which it was at first 
referred. But this allocation has proved to be incorrect, now that 
the osteological structure of the minute Fish (only about 3 
mm. long) has been worked out by Swinnerton.' The vertebrae 
number 42 to 45 (28—30+14-—15). A long, slender air- 
bladder is present. 
* 
Sub-Order 2. Ostariophysi. 
Air-bladder, if well developed, communicating with the digestive 
tract by a duct. Pectoral arch suspended from the skull; meso- 
coracoid arch present. Fins without spines, or dorsal and pectoral 
with a single spine formed by the co-ossification of the segments of 
an articulated ray. The anterior four vertebrae strongly modified, 
often co-ossified and bearing a chain of small bones (so-called 
Weberian ossicles) connecting the air-bladder with the ear. 
This is one of the most natural groups of the Class Pisces, 
although its members are so diversified in outward appearance 
as to have been widely separated in the systems of older authors. 
It is to Sagemehl” that is due the credit of having first grouped, 
under the above name, the Characines, the Carps, the Cat-Fishes, 
and the Gymnotids, the relations of which had been realised, 
to a certain extent, by Cope. But it was not until the homology 
throughout the group of the ossicula auditus, first described by 
E. H. Weber in 1820, had been demonstrated by Sagemehl that 
the justification for the course here followed appeared in its full 
1 Zool. Jahrb. Anat. xviii. 1903, p. 58. 2 Morphol. Jahrb, x. 1885, p. 22. 
