28 



suture line is optically similar to sutures other than that of the line of 

 cell-division which is more heavily marked. 



The appended tabic of diagnostic chaiv 'jiers based on measurments 

 of a number of individuals will serve more clearly to define the charac- 

 ters of the species in question. iS'orthern forms (Alaskan) are .absolutely 

 larger in dimensions of the midbody than southern (San Diego), but 

 horns, especially the apical, tend to be relatively longer in the indivi- , 

 duals from warmer waters. ^ 



Both C. linmtniii and C. furca are common cosmopolitan species 

 alike in neritic and oceanic plankton. C. eugrammum is likewise cos- 

 mopolitan and C. Inrs bids fair to exhibit a similar range as it is wide- 

 spread in Pacific waters. These two species are, however, both relati- 

 vely rare, perhaps in part because of the fact that their small size permits 

 them to slip through the mesh of the silk gauze used in plankton nets. 



A few filter catches which I have examined have not indicated any 

 abundance of these two species equal to that of C. furca and C. line- 

 atum. They are apparently not well established dominant species and 

 perhaps belong in the category of less sturdy mutants from some member 

 of the C. furca group. 



Berkeley, California, March 23, 1907. 



