GILL] THE FAMILY OF CYPRINIDS 197 
on, occur wherever any other Eventognaths do. The Cobitids are 
mainly Asiatic, but several are African and three species have 
extended into Western Europe. The Homalopterids are confined 
to India and the continent and islands to the eastward. 
CHARACTERISTICS OF THE CyPRINIDS 
The form varies from high as in the breams and catlas to elongate 
as in the American Phenacobius and Platygobio and the African 
Chelethiops, the belly being generally rounded, rarely (as in the 
sichling and Chelethiops) compressed and trenchant; the scales are 
cycloid, confined to the body (not extending onto the head)—trarely 
wanting ; the lateral line is more or less decurved and parallel with 
the belly, rarely atrophied; the fins, especially the dorsal and anal, 
vary greatly in size and relative position. 
The carp-like fishes are the “leather-mouthed fish” of Izaak 
Walton; they have no teeth in the jaws, but to some extent divide 
or prepare their food by the operation of teeth on the concave side 
of the sickle-like pharyngeal bones which are just behind the gill- 
arches. The character was long ago observed but not understood 
and fishes distinguished thereby were designated by the English 
fishermen as “ leather-mouthed.” 
“ By a leather-mouth,” Walton explained, “I mean such as have 
their teeth in their throat, as the chub or cheven, and so the barbel, 
the gudgeon, the carp, and divers others have.” These “teeth in 
their throat’ are, as just remarked, really on special bones behind 
the gills called “ pharyngeal.” 
The pharyngeal bones and especially the teeth which beset them, 
are so much used in classification that a little attention to them is 
called for here. They were first utilized for the arrangement of 
the genera by Agassiz (1835) and later much more extensively by 
the Austrian naturalist, J. Heckel (1843) and ever since have been 
made use of in all works treating of these fishes. 
The pharyngeal bones are not only immediately behind the 
branchial arches, but are considered to be “ serially homologous ” 
with them; in other words, derived from primitive generalized 
arches but greatly modified from them. They tend to preserve the 
' same general form as the arches and are more or less falciform, 
or like a sickle, having a short base of insertion or handle and an 
ample arched body. In the suckers or Catostomids these bones are 
provided with numerous processes or teeth inserted at right angles 
to the axis of the bone. In the carp-like or Cyprinoid fishes, the 
teeth are in reduced number and variously modified. There is 
