The benthic polychaetous annelids of Bahía de los Angeles were studied quantitatively in April 1962 and October 1963. Distribution and sediment preferences of the principal species are summarized. Of the 112 species encountered, ninety were previously unreported from the Gulf ol California. Six new species are described:
Microphthalmus riojai, sp. n.,
Aricidea (Aricidea) rosea sp. n.,
Prionospio longibranchiata sp. n.,
Pectinaria (Pectinaria) hartmanae sp. n.,
Euchone barnardi sp. n., and
Euchone cortezi sp. n. In April 1962, 39,470 specimens were collected; in October 1963, 7,100. The cause of this reduction is unknown, but high summer water temperatures may be involved. Previous reports of polychaetes from the Gulf of California are summarized.