COPEPODS FROM EQUATORIAL WATERS OF PACIFIC OCEAN 



181 



Eucalanus suhtenuis Giesbrecht, 1888 



(Plate 2, figs. 19-21; Plate 3, figs. 1-4) 



Pacific records: Ver\'oort, 1946. Also, Mori, 1937; 

 Tanaka, 1935a; Johnson, 1942; Mori, 1942; Wilson, 

 1942; 1950; Tanaka, 1953; 1956a; Fukase, 1957; Honjo 

 et al., 1957; Heinrich, 1958b. 



Vessel: Station Occurrence 



Hugh M. Smith 94 1 female, 3.12 mm. 



Do 132 13 females, 2.55-2.96 



mm. 

 Do 144 10 females, 2.40-2.60 



mm. 



Do 153 present. 



Do 178 15 females, 2.65-2.72 



mm.; 6 males, 



2.45-2.52 mm. 

 Do 31 15 females, 2.55-2.79 



mm. 



Do 63 16 females, 2.69-2.96 



mm.; 1 male, 2.51 



mm. 



Remarks: All of the present specimens are 

 referable to E. suhtenuis var. japonica Fukase, 

 1957. This variety is distinguished from stib- 

 tenuis chiefly by the number of setae on the 

 mandibular palpus (both sexes) and the struc- 

 ture of the fifth feet of the male. There are 

 3 setae on the mandibular palpus (fig. 21 ; fig. 

 3) and the distal segment of the fifth foot is 

 longer than the terminal spine (fig. 4). In 

 suhtenuis there are 2 setae on the mandibular 

 palpus and the tei'minal spine of the fifth foot 

 is longer than the distal segment. 



According to Fukase, Tanaka's (1935a) E. 

 suhtenuis and Mori's (1937) E. mucronatus are 

 both referable to siihtenuis var. japonica. 



This species was present in seven of the 

 samples and in four of these (Smith 132, 144, 

 178, 63) it was the most abundant species. 



Eucalanus pileatus Giesbrecht, 1888 



(Plate 3, figs. 5-12) 



Pacific records: Scott, 1909; Tanaka, 1935a; Wilson, 

 1950; Tanaka, 1953; 19.'36a. 



Vessel : Station Occurrence 



Satsuma 32 2 females, 1.80 and 



1.94 mm. 



Remarks : This species closely resembles E. 

 subcrassus and the two may prove to be con- 

 specific. Until a detailed study is made of each, 



it seems best to keep them separate. The fe- 

 males may be distinguished as follows (Pacific 

 specimens) : 



1. Size. E. pileatus, 1.80-2.41; E. subcras- 

 sus, 2.23-2.82. (length data from Tanaka, 

 1935a; Mori, 1937; Vervoort, 1946; and pres- 

 ent data) . Farran (1936) has reported E. sub- 

 crassus with total lengths of 1.84-2.92 from 

 the Great Barrier Reef. He did not record 

 E. pileatus. 



2. Shape of forehead. In dorsal view an- 

 terior end of forehead more produced in E. 

 pileatus (fig. 7) than in E. subcrassus (plate 

 3, fig. 15). 



3. Shape of genital segment. E. pileatus, 

 greatest diameter at a point approximately 

 one-half the length of the segment (fig. 10) ; 

 E. subcrassus, greatest diameter in lower third 

 of segment (plate 3, fig. 16). 



Eucalanus subcrassus Giesbrecht, 1888 



(Plate 3, figs. 13-17) 



Pacific records: Vervoort, 1946. Also, Tanaka, 

 1935a; Mori, 1937; 1942; Wilson, 1950; Anraku, 1952; 

 Honjo, 1952; Tanaka, 1953; Anraku, 1954b; Tsuruta 

 and Chiba, 1954b; Brodsky, 1955; Chiba, Tsuruta, and 

 Maeda, 1955; Motoda and Anraku, 1955; Nagaya et al., 

 1955; Rose, 1955; Tanaka, 1956a; Honjo et al., 1957; 

 Yamazi, 1958a. 



Vessel: Station Occurrence 



Hugh M. Smith ._ 63 3 females, 2.44-2.52 



mm. 



Stranger 34 3 females, 2.24-2.48 



mm. 



Orso7n 10 4 females, 2.31-2.48 



mm., 3 males 

 (stage V), 2.11- 

 2.18 mm. 



Remarks: Vervoort (1946) stated that there 

 are 4 setae on the second basal joint of the first 

 maxilla. The present specimens, however, have 

 5 (fig. 17). 



Rhhicalanus cornutus (Dana, 1849) 



(Plate 3, figs. 18-19) 



Pacific records: Vervoort, 1946. Also, Yamada, 1933; 

 Tanaka, 1935a; Mori, 1937; 1942; Wilson, 1942; 1950; 

 Honjo, 1952; Tanaka, 1953; Anraku, 1954b; Tsuruta 

 and Chiba, 1954b; Chiba, Tsuruta and Maeda, 1955; 

 Hida and King, 1955; Nagaya et al., 1955; Rose, 1955; 



