THE CYPRINOIDS 167 



they are connected by ligament with the tripus, 

 which is the modified rib of the third vertebra, 

 inserted in the wall of the air-bladder, and in this 

 connecting ligament appears the intercalarium, which 

 is the neurapophysis of the second vertebra. The 

 functions of this mechanism are not well ascertained, 

 but it is probably the case that by its means the 

 perception of sounds, movements, or alterations of 

 pressure is intensified. 



The Carp family (Cyprinidce) is probably richer 

 in species than any other family of fishes, consider- 

 ably more than one thousand having been described 

 from the lakes and rivers of Europe, Asia, Africa, 

 and North America. They are fishes with a 

 naked head, and usually a scaly body, and with 

 all or most of the fin-rays jointed and flexible. 

 The pectoral fins are placed low, the pelvic fins 

 are abdominal in position, and there is no adi- 

 pose fin. The mouth is toothless, more or less 

 protractile, bordered above by the prasmaxillaries 

 only, and the gill-membranes are usually joined to 

 the isthmus, restricting the gill - openings from 

 below. Most characteristic of the family are 

 the falciform lower pharyngeal bones, bearing a 

 small number of teeth which bite upwards against 

 a hard plate attached to a backwardly directed 

 process of the basal part of the skull ; the form of 

 these pharyngeal teeth, their number and their 

 arrangement in one, two, or three series are of 

 great importance in the distinction of genera and 

 species. 



All our Cyprinoids are more or less gregarious ; 

 they usually subsist on a mixed diet, but some, like 



