98 F. Day — Monograph of Indian Cyprinida. [No. 2, 



Having completed my descriptions, the next question for con- 

 sideration was the most appropriate mode of arrangement, and 

 though I have not separated, as families, the cyprinin^e from the 

 cobitidin^, and these again from the HOMALOPTERiNiE, much less 

 distinctive characters, than existing between these divisions, appear 

 to have lately found favour for this purpose in ichthyology. The 

 species with an air-bladder free in the abdominal cavity, those 

 with one partially or entirely enclosed in bone, and lastly those 

 destitute of this organ, are in the present communication merely 

 classed respectively in three sub-families of the Cypbinid^. 



Commencing with the sub-family CYPumiNiE, as existing in Asia, 

 considerable difficulty arises in selecting from amongst the various 

 groups into which it has been divided. Too much space, however, 

 would be occupied were I to enter upon a minute investigation of 

 the systems of others, and the reasons why I have found myself 

 unable to adopt them. 



In forming groups, one of the first characters may be found by 

 observing whether the scaled edge or margin of the abdomen is 

 rounded or cutting, for in the majority of the Indian cyppinin^e the 

 abdominal edge is rounded or smooth, even when somewhat com- 

 pressed, whilst in a few genera the abdominal edge posterior to the 

 ventral fin is compressed, cutting, and may be even serrated, as in 

 the CLUPELDiE ; this trenchant edge in some is continued from in 

 front of the ventral fin to the thorax. 



Irrespective of the above, there are many other characters which 

 might be employed for forming sub-groups and genera. In some, 

 however, which might at first appear suitable for such purposes, 

 one fails to attach that significance to their existence when large 

 numbers of species come under review, showing the existence of 

 connecting links. Some of these characters may be external, others 

 are internal. 



The mouth is variously formed ; it may be transverse and inferior, 

 with or without a sucker, the latter being present either on the 

 lower lip only or existing on both ; or it may be narrow, of medi- 

 um size ; or wide : anterior, and either antero-lateral or oblique. 

 The lower jaw again may be prominent, sharp or rounded, shorter 

 than the upper, or sometimes having a knob at the symphysis ; a 



