1911] Michael: Chaetognatha of the San Diego Region. 115 



E. hamata 72 



E. subtilis 50 



S. planktonis 41 



S. hexaptera 28 



S. draco 1 



Owing to the fact that S. hipunctata is the most abundant, 

 it is best to consider its manner of distribution first. 



VERTICAL DISTRIBUTION OF SAGITTA BIPUNCTATA. 



Of the total number of this species obtained, 32,601 were 

 taken from the surface, 17,144 in open vertical nets from depths 

 varying from 2 to 500 fathoms, 303 in vertical closing nets from 

 between 150 fathoms and the surface, and 1,322 in horizontal 

 closing nets. Neglecting those obtained with open vertical and 

 vertical closing nets, we find that from July 23, 1904, to April 

 21, 1910, 148 surface hauls were made, of which 108, or 72 per 

 cent, obtained the 32,601 specimens mentioned. The horizontal 

 closing nets obtained a total of 283 specimens in 7 out of 11 

 hauls made between 4 and 6 fathoms, 71 in 6 out of 15 hauls 

 between 7 and 12 fathoms, 683 in 13 hauls between 15 and 20 

 fathoms, 128 in 8 out of 19 hauls between 25 and 35 fathoms, 

 147 in 6 out of 20 hauls between 40 and 75 fathoms, and 10 in 

 4 out of 19 hauls between 100 and 150 fathoms. Although 21 

 hauls were made between 160 and 350 fathoms, the species was 

 not obtained. These data are shown to better advantage in the 

 following table. 



TABLE 36 



Vertical Distribution of S. bipunctata based on Surface and Horizontal 



Closing Net Hauls 



Depth Number of hauls^ Number of Number of specimens 



in > '■ ^ hours of , " ., 



fathoms Total Successful hauling Total Per hour Frequency^ 



136 96 96.7 29,696 307 70 

 4-6 11 7 3.3 283 92 64 

 7-12 15 6 4.6 71 15 40 



15-20 13 13 3.5 683 195 100 



25-35 19 8 5.3 128 24 42 



40-75 20 6 5.7 147 26 30 



100-150 19 4 6.5 10 2 21 



160-350 21 9.0 



1 The durations of hauls 216-1416 are unknown, and they are, therefore, 

 not included in this table. 



- By frequency is meant the percentage of hauls in which the species 

 appeared without reference to abundance of specimens obtained. 



