Heterorhabdus abyssalis (Giesbrecht, 1889) 

 (Plate 11, figs. 1-6) 



OccuiTence 



Sta. 9. 3 adult females, 2.47 to 2.69 mm. ; 

 1 adult male, 2.41 mm. 



Remarks 



This species is recognized by the rounded 

 forehead in lateral aspect (fig. 2) and the 

 structure of the maxilla (fig. 4), the distal lobe 

 of which has 2 spines of equal length and 1 

 slightly shorter spine. In the fifth pair of legs 

 of the female (fig. 3), the internal spine of 

 the second exopodal segment is about as long 

 as the third exopodal segment and is fringed 

 with fine hairs along the upper margin. The 

 fifth pair of legs in the male (figs. 5 and 6) 

 is characterized by the laminar protrusion on 

 the internal margin of the right basis and the 

 conical internal projection of the second seg- 

 ment of the right exopod. 



Heterostylites longicornis (Giesbrecht, 1889) 



Occurrence 



Sta. 5. 2 adult females, 2.80 to 2.83 mm. ; 



1 adult male, 2.90 mm. 

 Sta. 7. 1 adult female, 2.90 mm. 



Remarks 



This species is closely similar to the species 

 of Heterorhabdus but can easily be distin- 

 guished from the latter by the longer anten- 

 nule, the armament of the mandibular blade, 

 and the better developed endopod of the max- 

 illa. In the female, the second exopodal segment 

 of the fifth leg has a compound spine, with 6 

 to 7 points, medial to the regular external 

 spine. 



H. longicornis is distinguished from H. major 

 only by its smaller size ; there are prac- 

 tically no anatomical differences. The female 

 of H. loiifiicornis. according to Giesbrecht and 

 Schmeil (1898), measures about 3.0 mm., but 

 that of H. major measures about 5.0 mm. 



FAMILY AUGAPTILIDAE 



Haloptilus longicornis (Glaus, 1863) 

 Occurrence 



Sta. 3. 136 adult females, 2.00 to 2.24 mm. 

 Sta. 5. 44 adult females, 2.17 to 2.44 mm. 



Sta. 7. 3 adult females, 2.14 to 2.34 mm. 



Remarks 



This species was one of the most common 

 at the southern .stations, but not a single male 

 was found. The female can be recognized by 

 the knoblike projection on the forehead, 

 when viewed from above, and the very long 

 antennule. 



Haloptilus fertilis (Giesbrecht, 1892) 



(Plate 11, figs. 7-20) 



Occurrence 



Sta. 3. 2 adult males, 2.89 to 3.16 mm. 

 Sta. 5. 3 adult males, 2.93 to 3.13 mm. 



This species was erected on the basis of a 

 male from the Mediterranean Sea (Giesbrecht, 

 1892). Grice (1962) obtained a single male 

 from equatorial waters of the Pacific. The fol- 

 lowing description is based on the five adult 

 males in the present collections. 



Description of Males 



The total length ranges from 2.89 to 3.16 mm. 

 The proportional lengths of the prosome and 

 urosome are about 5.6:1. The first metasomal 

 segment is separated from the cephalosome, but 

 the fourth and fifth metasomal segments are 

 fused. The cephalosome in dorsal aspect has a 

 broadly triangular forehead, and the oral 

 region is more or less dilated. The postero- 

 lateral margins of the metasome are smoothly 

 rounded (fig. 7). 



The urosome (fig. 8) is 5-segmented. The 

 first segment is nearly as long as the combined 

 lengths of the succeeding 3 segments. The fig- 

 ure by Giesbrecht (1892, plate 42, fig. 5), how- 

 ever, shows the second to fourth urosomal seg- 

 ments relatively longer than those of the pres- 

 ent specimens. 



The right antennule is normal, 25-segmented, 

 and reaches as far as the end of the caudal 

 ramus. The 23-segmented left antennule (fig. 

 9) is modified for grasping the female. Each 

 of the 14th to 16th segments has a swollen 

 outer margin, and each of the 17th to 19th 

 segments has a serrated lamella along the same 

 margin. A knee joint is found between the 18th 

 and 19th segments. 



In the antenna (fig. 10), the exopod is only 

 about one-third the length of the endopod. The 



CALANOID COPEPODS FROM NORTH PACIFIC 



561 



