margin, and the third segment has 3 small 

 spines on the posterior surface. 



The fifth leg (fig. 9) is uniramous and 4- 

 segmented. The segments have the proportional 

 lengths of 35:13:17:35. The fourth segment 

 has 1 distally situated external spine, 1 termi- 

 nal spine, 2 distally situated internal setae, and 

 a row of spinules at the bases of these spines 

 and setae. As shown in figure 9, the right and 

 left legs are different in the lengths of the ex- 

 ternal spines and the upper internal setae. 



Remarks 



Calocalamis tenvis was first described from 

 the Bay of Biscay by Farran (1926) ; it has 

 not been reported from the Pacific. The speci- 

 mens in the present collections are poor, be- 

 cause some appendages are broken ofi!'. They 

 are, however, readily recognized by the slender, 

 fusiform body and the characteristic shape of 

 the fifth leg. 



FAMILY PSEUDOCALANIDAE 



Pseudocalanus minutus (Kroyer, 1848) 

 Occurrence 



Sta. 16. 1 adult female, 1.26 mm. 



Clausocalanus arcuicornis (Dana, 1849) 

 (Plate 4, figs. 10-13) 

 Occurrence 



Sta. 3. 7 large females, 1.51 to 1.60 mm. ; 

 14 small females, 1.38 to 1.48 

 mm. ; 



2 males, 1.40 mm. 



Sta. 5. 4 large females, 1.51 to 1.58 mm. ; 



3 small females, 1.12 to 1.41 mm.; 

 1 male, 1.28 mm. 



Sta. 7. 6 large females, 1.50 to 1.55 mm.; 



5 small females, 1.12 to 1.46 mm. 

 Sta. 9. 4 large females, 1.58 to 1.70 mm.; 



3 small females, 1.28 to 1.50 mm. ; 



1 male, 1.42 mm. 

 Sta. 13. 7 large females, 1.65 to 1.83 mm.; 



20 small females, 1.37 to 1.58 

 mm. ; 



1 male, 1.23 mm. 

 Sta. 15. 5 large females, 1.68 to 1.83 mm.; 



21 small females, 1.20 to 1.51 

 mm. ; 



1 male, 1.14 mm. 



Sta. 16. 5 small females, 1.28 to 1.31 mm.; 

 1 male, 1.46 mm. 



Remarks 



Sewell (1929), who studied material from 

 the Indian Seas, divided females of C. arcui- 

 cornis into two forms, namely f. minor and f. 

 major, mainly diff"ering in the structure of the 

 fifth pair of legs and the proportional lengths 

 of the prosome and urosome. Grice (1962) 

 found two female forms of this species in the 

 equatorial Pacific and tentatively identified 

 these with the two forms described by Sewell 

 (1929). The females of the present collection 

 also fall into two groups that are separable 

 mainly by the total lengths and the shapes of 

 the fifth pairs of legs. 



The total lengths of the large form range 

 from 1.50 to 1.83 mm. The prosome is 2.7 to 3.1 

 times as long as the urosome. In the fifth leg 

 (fig. 10), the proximal segment is stouter and 

 is longer than or as long as the following seg- 

 ment, and the terminal segment is shorter than 

 the preceding two segments combined. The gen- 

 eral shape of the fifth pair of legs is similar 

 to that of f. major described by Sewell (1929), 

 but my specimens are much larger than the 

 1.17 mm. reported by him. 



The total length of the small form is 1.12 to 

 1.58 mm. The proportional lengths of the pro- 

 some and urosome are about equal to those in 

 the large form. The proximal segment of the 

 fifth leg (fig. 11) is slightly narrower and is 

 shorter than the following segment. The termi- 

 nal segment is longer than or as long as the 

 preceding two segments combined. This small 

 form seems to correspond to f. major described 

 by Grice (1962) in total length and shape of 

 the fifth pair of legs, but is not identical with 

 Sewell's major in shape of the fifth pair of legs. 



Two females from station 9 had abnormal 

 fifth pairs of legs (figs. 12 and 13). 



Clausocalanus pergens Farran, 1926 

 (Plate 4, figs. 14 and 15) 



Occurrence 



Sta. 7. 1 adult female, 0.85 mm. 

 Sta. 13. 1 adult female, 0.94 mm. 



Remarks 



This species can be distinguished from C. 



CALANOID COPEPODS FROM NORTH PACIFIC 



541 



