MARINE ZOOLOGY 



767 



from Matagorda and out from Port Aransas show a high degree 

 of salinity. The readings range from 36.6 to 37.1 parts of salt pei* 

 one thousand. The average given for the Atlantic Ocean is be- 

 tween 35 and 36 parts per one thousand. These readings on the 

 Gulf are being checked by further data, but the cause of this dif- 

 ference has not been explained. 



The salinity of the bays is quite variable, and Galtsoff in 1926 

 made comparative studies of a number of them. It was found that 

 in bays with a large fresh-water stream entering, as Nueces Baj^ 



;T— L/mbrella 



// 



-Manubrium 



7mm- 



y/M oral 

 ~^ tentadei 



■ Central moufch 



Fig. 403. 



-Cabbage-head jellyfish, Stoviolophus meleagris, a very common form in 

 the Gulf of Mexico. 



the range is from 6.06 parts per thousand in June to 33.06 parts 

 per thousand in September. In Mesquite Bay at Belden Dugout 

 Beacon the range is from 5.03 parts per thousand in June to 18.44 

 parts per thousand in October. In Aransas Bay, where there is 

 relatively small fresh-water intake, the salinity ranges on the aver- 

 age between 14.79 parts of salt per thousand in June and 25.47 parts 

 per thousand in September. 



These wide ranges of salinity in the bays create problems for the 

 organisms attempting to live there. It requires a high degree of 



