Figure 6. — Designated sites (represented by a dot) occur- 

 ring at frequencies of ^80% within the pattern of each 

 species and present in every species of the genus 

 Eiicalanus. Dorsal view on left, lateral view on right; 

 outline of organism based on elongaius used solely as 

 vehicle to show topographic relationships of sites. 



The Subtenuis Group 



Sites distinguishing the subtenuis group 

 (Figure 8c) appear on various portions of the 

 cephalosome and thorax. On the cephalon the 

 mandibular somite bears two pairs of tergal 

 sites. ThI shows only three sites arranged in a 

 transverse row. ThIII and ThIV are similar, 

 both being characterized by bilateral tergal 

 pairs lying outside and anterior to the quadran- 



FISHERY BULLETIN: VOL. 71, NO. 4 



gle of hair sensilla and a single medial site 

 slightly posterior to the anterior hair sensilla. 

 The subtenuis group contains five generally 

 accepted species that occur typically in eutroph- 

 ic oceanic waters. 



Sites in E. crassiis (Figure 9a) are identical 

 with the pattern of the species group except that 

 the perforations of row a on the mandibular 

 somite are increased to two pairs (Mnd T-a-/l, 

 12 and rl, r2). 



E. lo)igiceps differs from the group pattern 

 solely by the presence of a single mediodorsal 

 site on the genital segment (Figure 9b). 



E. m(>}iachus (Figure 9c) differs from longi- 

 ceps in two features: the occurrence of a trans- 

 verse row of three tergal sites across Abd.IV-V 

 and three pleural sites on Thll, ThIII, and 

 ThIV. 



E. })iucr(>}iatus (Figure 9d) shows a small 

 increase in the number of sites. On the cepha- 

 losome up to six pairs of tergal sites may appear 

 in addition to the group number between the 

 somite of the second maxilla and the maxilli- 

 pedal somite. ThI shows an additional tergal 

 pair on either side of the middorsal site. Thll 

 and ThIII have an additional site in the posterior 

 row (Thll T-b-/l and ThIII T-b-/l) to the left, 

 but the symmetrical homologue to the right of 

 the middorsal axis is absent. On the abdomen 

 the genital segment has two middorsal sites 

 and Abd.III may have one. 



E. subtenuis (Figure 9e) has the largest num- 

 ber of regular perforation sites in the genus. 

 Dorsally, in addition to the species group num- 

 ber, two more pairs appear in the somite of the 

 second antenna, up to eight more pairs between 

 the somites of the first and second maxillae, 

 four more pairs on the maxillipedal somite, 

 four more pairs on ThI, and two more pairs on 

 Thll. Thll and ThIII have a single asym- 

 metrical tergal site (pore) within the quadrang- 

 le formed by the hair sensilla as in niucrojiatus. 

 Laterally, Thll and ThIII both show one or 

 more pairs on either side. 



Within the groui^, snbfeiiiiis shows the largest 

 number of perforations (Figure 10) and the 

 most extensive geographical distribution relative 

 to areal extent and sympatry (unpublished). 

 Differences between subtenuis and its closest 

 cognate, niucronatus, are concentrated in the 



982 



