FISHERY BULLETIN: VOL. 71. NO. 4 



3.0 



£ 

 E 



2.0 



□ subcrossus 

 I dentatus 

 S pi leaf us 



n 



n  



^ 



• V. 



i 



i 



80 



90 100 



PERFORATION NUMBER 



10 



20 



Figure 12. — The pileatus group of Eucalanus. Perforation number plotted against total length (TL) in adult females com- 

 prising the pooled samples. 



As in the two preceding species groups a re- 

 lationship between distinctiveness in overall 

 number of perforations and geographical distri- 

 bution is shown by the elongatus group (Figure 

 14). The only circumglobal species of the group, 

 hyaliiius, occupies a distinctive position with 

 respect to perforation number. The two species 

 to the left, iiiermis and idongatus, are geo- 

 graphically isolated from one another and the 

 two species to the right, biiiigii and californicus, 

 are biogeographically separated from one an- 

 other. The distribution of hifalinns in contrast 

 brings reproductively ripe individuals into 

 contact with all of the other species except bnii- 

 gii (unpublished data). 



The Attenuatus Group 



Members of the attenuatus group have in 

 common 38 tergal and 8 pleural sites added to 



the primary generic number (Figure 8b). The 

 increase is widely dispersed about the body being 

 found anteriorly on the second antennal somite 

 (A2T-a-/l. 12 and rl. r2). the somite of the 

 second maxilla (Mx2T-/l, 12 and rl, r2) and on 

 the maxillipedal somite, where six pairs occur, 

 two pairs more than in the elongatus group. 

 Adding to the characterization are the anterior 

 middorsal pair of ThI, the six symmetrically 

 arranged tergal sites of ThV and the three tergal 

 sites of Abd.IV-V. In lateral view pleural sites 

 are also more numerous, three pleural sites on 

 each side being found on Thll, ThIII, ThIV, 

 and on the genital segment. Every segment 

 except Abd.III bears more sites than the num- 

 ber characterizing the genus, and the group 

 total of 109 sites is the largest among the four 

 groups of species in Eucalanus. 



Four discrete populations of attenuatus s.l. 

 emerge from the present study. They are mor- 



988 



 



