Hello ,

Features of class cyclostomata :

• The cyclostomes are jawless fishes.
• They have suctorial tongue .
• Endoskeleton is cartilaginous
• Notochord is persistent throughout life
• Elongated body bearing 6-15 pairs of gill slits for respiration
• Heart is 2-chambered
• Ectoparasites
• External fertilization
• Ammocoetes larvae may be seen
• Example : Petromyzon and Myxine

Hope this helps