268 Unu'crsity of Califoniia Publications in Zoology [Vol. 15 



The average seasonal variation in temperature at all deptlis less 

 than five hundred meters during the period from 1908 to 1915 is 

 shown by plate 26, figure 45. This, together with plate 25, figure 40. 

 shows that the month of minimum temperature varies from February 

 at the surface to May at depths exceeding thirty meters, and that the 

 month of maximum temperature varies from August at the surface to 

 November at depths exceeding fifty meters. It also shows tliat the 

 annual range in temperature decreases from 6?2 C at the surface to 

 1:0 C at two hundred meters, while it can scarcely be detected below 

 four hundred meters. 



The average seasonal variation in salinitj' at all depths less than five 

 hundred meters is shown by plate 26, figure 46. Though salinity data 

 are very deficient for October, November, December, and January, and 

 are less complete than the temperature data for the remaining months, 

 certain general facts can be inferred. At the surface (see also pi. 25, 

 fig. 43) the minimum salinity occurs in February and the maximum 

 in July or August. At 25 meters a minimum annual range of 0.15''/„,) 

 is shown. Below 75 meters the maximum occurs in April, and the 

 minimum in November; while the annual range at 150 meters ap- 

 proximates to 0.25°/,„„ the range at the surface. Below 400 meters 

 the annual range can scarcely be detected. The peculiar dip of all 

 isohalines below 50 meters between May and. July is very likely due 

 to a difference in years rather than months. 



The distribution of temperature and salinity is very different in 

 spring, when the increasing solar radiation tends to raise the temper- 

 ature and salinity, from that in autumn, when because of the de- 

 creasing solar radiation the water tends to cool. In fact, there is a 

 characteristic distribution of temperature and salinity for each month 

 which is revealed in detail by plates 27-32. 



The surface temperature of Glorietta Bight, a shallow inlet of 

 San Diego Bay near Coronado Beach, well removed from direct influ- 

 ences of the main tidal currents, has an annual range of 10° C, from 

 a minimum of 14° C in January to a maximum of 24° C in July or 

 August (pi. 33, fig. 92). The corresponding surface salinity (pi. 33, 

 fig. 91) has an annual range of 1.73''/o(„ seven times greater than in 

 the ocean. It varies from a minimum of 33.67V„|, in February to a 

 iiuiximum of 35.40'V„„ in July. Temperature observations made in 

 the central portion of the bay reveal an annual range (pi. 33, fig. 93) 

 of 9?7 C from a minimum of 12? 8 C in January to a maximum of 

 22? 5 C in August. 



