Published in Zoology
Wednesday, 28 June 2017 15:49
The class Cyclostomata is divided into two orders:

1) Petromyzonia and 2) Myxinoidea
Order 1: Pefromyzonia
  1. Lampreys are included in this order.
  2. The buccal funnel is suctorial and shows horny teeth.
  3. The mouth is present in the buccal funnel.
  4. The nasal sac is dorsal. It has no connection with the pharynx.
  5. Eyes are functional.
  6. Seven pairs of gill slits are present.
  7. A well developed dorsal fin is present.
  8. Branchial basket is complete.
  9. Brain is well developed.
  10. Pineal eye is well developed.
  11. Ear has two semicircular canals.
Ex: 1. Petromyzon (Sea-lamprey) Lampetra fluviatilis.
Order 2: Myxinoidea
  1. It includes the hag-fishes or slime eels.

    hagfish Myxini 218

  2. Buccal funnel is absent.
  3. The nasal sac open into pharynx, through a canal.
  4. Eyes are vestigial organs.
  5. Dorsal fin is absent or very small.
  6. Branchial basket is poorly developed.
  7. Brain is primitive.
  8. Pineal eye is reduced.
  9. Ear has only one semicircular canal.
  10. The hag-fishes are all marine.
Ex: 1. Myxine glutinosa (Hag-fish or slime eel). 2. Eptatretus (Bdellostoma)

Useful Sites

  • NCBI

    National Center for Biotechnology Information
  • LTO

    Lab Tests Online® by AACC
  • ASCP

    American Society for Clinical Pathology
  • ASM

    American Society for Microbiology
  • The Medical Library®

    Project of

Connect With Us

Contact Us

All comments and suggestions about this web site are very welcome and a valuable source of information for us. Thanks!

Tel: +(92) 302 970 8985-6

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.


This website is certified by Health On the Net Foundation. Click to verify. This site complies with the HONcode standard for trustworthy health information:
verify here.

Our Sponsors

InsightGadgets.comPathLabStudyTheMedicalLibrary.orgThe Physio

By using you agree to our use of cookies to enhance your experience on this website.