6 



PROCEEDINGS OF THE NATIONAL MUSEUM 



Superaorbital cirri: The number of free tips, all branches included, 

 of the cirri above the eye. The cirri generally have a common trans- 

 verse base. Counts of lateral or mesial cirri exclude the tip of the 

 main or longest cirrus (see measurements above) and include only 

 those cirri on the lateral or mesial margins of the main cirrus. 



Nuchal cirri: The number of free tips, all branches included, of 

 cirri on the side of the nape. 



In some specimens (for example all E. macrospilus) the nuchal 

 cirri are absent. The normal position for nuchal cirri can be recog- 

 nized by the position of a pair of pores on each side of the nape. 

 These pores lie on a slight transverse depression (constriction) 

 which more or less separates the head from the body dorsally. In 

 specimens with nuchal cirri the pores are just lateral to the cirri. 



Figure 1. — Diagrammatic illustration of pores included in predorsal commissural group 

 (solid dots) and other pores (open dots). 



Predorsal commissural pores (fig. 1): A count of all pore openings 

 in the region anterior to the first dorsal spine and between the bases 

 of the nuchal cirri, extending anteriorly on top of the head a distance 

 usually about one-half the head length or less. Anterior to the 

 level of the nuchal cirri the area occupied by the pores frequently 

 spreads laterally in both directions and covers an expanse broader 

 than the internuchal cirri distance; all pores anterior to the nuchal 

 cirri in this midregion are included in the count. In some specimens 

 this is a difficult count to make. Overlying mucus must be removed 

 and drying of the area is recommended. Inserting a tiny insect pin 

 into each pore will greatly facilitate making counts. 



