No. 553] DISTRIBUTION OF THE CH2ETO GNATHA 39 



Veak and thin. 

 r ery large. 



length of anima 



Doubtless the number of differences could be increased 

 were we to search details, but the twelve set forth in the 

 above table sufficiently emphasize the fact that the two 

 species are fundamentally distinct from a morphological 

 point of view. It would, in fact, be difficult to find any 

 species within the genus more differentiated from S. 

 euflata than is 8. neglecta. 



Looking to Group 2 of similar distributional species 

 and referring to the key (p. 35) we find that 8. bipunctata 

 is separable from S. hexaptera only by virtue of occurring 

 in large numbers and maintaining its maximum abun- 

 dance above 25 fathoms, whereas S. hexaptera occurs in 

 small numbers and maintains its maximum abundance 

 below 40 fathoms. In contrast to this we find that, 

 while 8. hexaptera occurs in Group 1 of similar morpho- 

 logical species, S. bipunctata occurs in Group 2. The fol- 

 lowing table, therefore, reveals their most fundamental 

 structural differences. 



TABLE IX 



hexaptera 



Length of body. 12-17 nun. when mature. 2 4- -55 mm. when mature. 



Width of body. 5-7 per cent, of length. 7.3-11 per cent, of length. 



Length of anterior fin. 15.9-23.7 per cent, of 8.6-11.8 per cent, of total 



