Chondrichthyes is one of the classes of super-class-Pisces, sub-phylum-Vertebrata and phylum-Chordata. The members of class-Chondrichthyes are marine animals with streamlined body and have cartilaginous endoskeleton. Mouth is located ventrally. The skin is tough, containing minute placoid scales. The teeth aremodified placoid scales which are backwardly directed, e.g., Dog fish (Scoliodon), saw fish (Pristis), great white shark (Carcharodon), sting ray (Trygon), etc.