WHILE ENUMERATING COPEPODS from net

hauls made in 1949 and succeeding years off the California coast in connection with the California Cooperative Oceanic Fisheries In-vestigation (CCOFI), it was observed that specimens with characters agreeing with those given in the literature for Calanus tenuicornis Dana were of two types. One form, limited to the southern portion of the area investigated, had a longer and narrower body and relatively longer appendages. The other, more stubby, form had a wider distribution, with maximum numbers to the north. The problem ofwhether these two forms are environmentally deter-mined or whether they differ genetically on the specific or subspecific level invited in-vestigation. The results of this study, pre-sented herein, have led to the conclusion that the more stubby form is Dana's C. tenuicornis, and the elongate form is a new species. Calanus tenuicornis was first described by Dana (1853: 1069) from the Central North Pacific. His description was brief, dealing chiefly with the first antenna. He figured (1855, pI. 73, fig. 10 a, b) a dorsal view of the adult female with the first antennae attached and detail of the distal end of the first antenna. Giesbrecht (1892, pIs. 6-8) provided several additional illustrations. Figures pub