xxii INTKODUCTIOK 



The Cyprinidiic may be divided into four sub-families, viz. Cypriniiife, Catostoraiiiffi, 

 Cobitidinse, and IIomalopterintE, the first having a range nearly co-extensive with that 

 of the family, the second being North American (with 2 or 3 species in Eastern Asia), 

 the third occurring in Eurasia and Abj'ssinia, the fourth in Southern Asia. 



The CypriniuEE, in addition to having the widest range, are by far the most diversified 

 and the most numerous in genera and species, and may perhaps be regarded as the 

 most generalized, especially as in some of tlie genera primitive characters are present 

 (pharyngeal teeth in more than one series, lips normal, gill-membranes free from the 

 isthmus, suborbitals broad) which are not to be found in the other sub-families. 



In the Cypriuimie the maxillaries are entirely or in great part excluded by the prfe- 

 maxillaries from the upper border of the mouth. The CatostomiucB differ from them 

 in that the margin of the upper jaw is formed in the middle by the small prsemaxillaries 

 and at the sides by the maxillaries; these bones are hidden in thick fleshy lips, and the 

 reduction of the praemaxillaries is, in my opinion, probably due to this fact. 



The Cypriuidse may have originated in some part of the Indian region *, which is at 

 the present day the richest in genera and species and where the most generalized forms 

 occur. Boulenger, regarding the Catostominaj as the most generalized group, considers 

 that the Cypriuida3 may have originated in North America as an offshoot of the South- 

 and Central-American Characinidie. He explains the fact that in America they have 

 not extended further south than Guatemala as due to competition with herbivorous 

 Characniids ; but as the most northern representative of the latter group {Curimatus 

 magdaleno:) does not extend further north than Panama, this explanation is scarcely 

 satisfactory, especially as Cyprinidae and herbivorous Characinidie are by no means 

 mutually exclusive in Africa. 



The Catostomints comprise about seventy species belonging to about ten genera from 

 North and Central America and three species belonging to about two genera from 

 Eastern Asia. 



Ictiolus, with the dorsal fin elongate, includes about twelve species, in rivers east of 

 the Rocky Mountains and the Sierra Madre, from tiie Great Lakes to the Ifio Usuma- 

 cinta in Guatemala. The Mexican species are four in number and are found in the 

 southern tributaries of the Ilio Grande and the rivers of Tainaulipas. /. mci'idionaUs 

 from the Usumacinta is the only member of the sub-family in the Neotropical liogion. 

 Cycleidiis, with a single species ranging from the Mississippi to Tamaulipas, and a 

 genus with two species in Cliina are allied to Ictiobtis. 



* The present distribiilion of (lie C'}priiiidiC leads to tlio supposition lliat they originated in Indo-China at 

 or before the beginniiijj of the Eoeene. 



