From the 30 families previously reported for San Quintin lagoon, 23 have been collected and 6 families were added: Ampharetidae, Oweniidae, Scalibregmatidae, Sternapsidae, Dorvilleidae and Sigalionidae.
The following families present in 1995 were not found in the 1998 survey: Dorvilleidae, Polynoidae, Oweniidae, Scalibregmatidae, Sternapsidae and Sigalionidae.
The proportion of families changed, some families disappeared completely in the 1998 survey: Dorvilleidae, Polynoidae, Oweniidae, Scalibregmatidae, Sternapsidae, Sigalionidae.
Eunicida sensu stricto Family Dorvilleidae Dorvillea cerasina (Ehlers, 1901): 12, 20, 21, 29, 34.
Polychaetous annelids of the families Eunicida, Lumbrineridae, Iphitimidae, Arabellidae, Lysaretidac and Dorvilleidae from western Mexico.