4 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
CHEMICAL AND PHYSICAL DATA.—Chlorinity was that of normal 
sea water throughout the sampled areas of Morro Bay. The chlor- 
inity probably is lowered in the vicinities of Chorro and Los Osos 
Creeks during the winter rainy season. 
Dissolved oxygen of the water ranged from 4.2 to 7.1 ppm with 
the lowest value measured at Station 10 and the highest at Station 
25. The oxygen values of the deeper waters were generally slightly 
higher than those of the surface readings. 
Temperature of the water ranged from 13.4° to 17.8° C on August 
26, 1960. The lower measurements were recorded at the entrance of 
Morro Bay and the higher values at Stations 23, 25, and 26. 
Sediments were not analyzed for particle size, but their condition 
was noted at the time of collection. In general, the sedimentary 
characteristics of Morro Bay may be divided into three catagories. 
Sands predominate at the entrance of the bay and extend to about 
the region of stations 7 and 8. Fine sediments and extensive patches 
of eel-grass, Zostera marina, and sea lettuce, Ulva sp., occur throughout 
much of the rest of the bay. The sediments of Chorro Creek, es- 
pecially at Stations 27 and 28, consisted primarily of gravels with a 
thin layer of silts and fine sands on top. 
THE POLYCHAETE FAUNA 
The polychaetes collected from the benthos of Morro Bay are 
listed in table 1 and are compared with those of other embayments 
of California and Baja California for which data are available. Of 
the 34 species taken, 18% or 55% also occur in San Francisco Bay. 
Less than 50% of the species are common with areas studied south of 
Morro Bay. 
New distributional data are recorded for seven species. The 
northern distribution is herein extended for three species from southern 
California, namely, Prionospio pygmaeus, Spiophanes massionensis 
and Pista alata. Cossura longocirrata is extended southward from 
Vancouver. Pseudopolydora kempi is reported from the eastern 
Pacific Ocean for the first time. With reservation, Magelona papil- 
licornis is reported from the Pacific Ocean for the first time. Chone 
infundibuliformis was reported from Elkhorn Slough by Berkeley and 
Berkeley (1935). No endemic polychaete was found in Morro Bay. 
Sphaerosyllis hystrix, Typosyllis fasciata, Boccardia polybrancha, 
and Spirorbinae have not been reported previously from the bay 
environments in the eastern Pacific Ocean. 
Four species account for over 70% of the 9127 specimens of poly- 
chaetes collected from the bay: Capitella capitata (2434), Streblospio 
benedicti (1999), Heteromastus filiformis (1078), and Exogone lourer 
