COPEPODS FROM EQUATORIAL WATERS OF PACIFIC OCEAN 



205 



tended and there is a distinct dilation on the 

 dorsal surface of the head. The rostrum is 

 straight and club-like (fig. 4). 



The first antennae of both specimens are 

 broken off near the proximal end. Although 

 somewhat mutilated, the second antennae ap- 

 pear to have 1 seta on the first segment of the 

 endopod. The second segment of the endopod 

 has 14 setae on the distal margin (8 on the in- 

 ner lobe and 6 on the outer lobe) . The exopod 

 has a total of 6 setae but some may be missing 

 from the various segments. 



The mandible has 3 setae on the basipod, 11 

 setae on the endopod and 6 on the exopod. 



The first maxilla (fig. 5) has the following 

 number of setae: 9 on the external lobe, 7 on 

 the exopod, 9 on the endopod, 5 on the second 

 basal segment, 2 on the second internal lobe and 

 3 on the third internal lobe. 



The terminal part of the second maxilla (fig. 

 6) has 6 sensory organs and 1 worm-like ap- 

 pendage. 



The exopods of the first 4 pairs of feet are 

 3-segmented (figs. 7-10), although the second 

 and third exopodal segments of the fourth pair 

 are broken off. The endopod of the first foot 

 consists of 1 segment, of the second foot of 2 

 segments and of the third and fourth feet of 3 

 segments. The endopodal segments of the sec- 

 ond and third feet have numerous spines aris- 

 ing from their posterior surfaces. A row of 

 spines is present at the junction of the first and 

 second basipodal segments, on the posterior 

 side, of the third and fourth feet. The fifth 

 foot (fig. 11) consists of 3 segments, all of 

 which are furnished with either marginal or 

 surface spines. 



Remarks : This species differs from other de- 

 scribed Xanthocalanus in (1) the dilations of 

 the dorsal surface of the head and lateral mar- 

 gins of the first thoracic segment, (2) the 

 spines on the basipodal segments of the third 

 and fourth feet, and (3) the details of the fifth 

 pair of feet. The fifth pair of feet closely re- 

 semble those of X. agilis Giesbrecht but agilis 

 lacks the characteristic dilations of the head 

 and first thoracic segment of the present spe- 

 cies. In addition. A', ac/ilis is a larger species 

 (2.40 mm.). The presence of spines on the 

 basipodal segments may also be found in other 



species of Xanthocalanus. Figures of these 

 segments are available for only a few species. 

 The name proposed for this species is derived 

 from the Latin word "dilato" and refers to the 

 characteristic protrusions on the head and first 

 thoracic segment. The holotype (U.S.N.M. No. 

 104, 420) and 1 paratype (No. 104, 421) have 

 been deposited in the U.S. National Museum. 



Amallophoru smilhae n. sp. 

 (Plate 15, figs. 12-22) 



Vessel: Station 



Hugh M. Smith — 144 __ 



Occurrence 

 1 female, 1.40 mm. 



Description: The head and first thoracic 

 segments and the fourth and fifth thoracic seg- 

 ments are fused (fig. 12). In lateral view the 

 posterior margin of the cephalothorax has a 

 small indentation (fig. 13). 



The first antennae are short and do not reach 

 the end of the cephalothorax. Each antenna 

 consists of 23 segments. 



The endopod of the second antenna is slightly 

 less than three-fourths the length of the exo- 

 pod. Endopodal segment 1 has 2 setae. Seg- 

 ment 2 has 8 setae on the inner lobe and 7 setae 

 on the outer lobe. The exopod has 8 setae all 

 of which are densely plumose. 



The basal segment of the mandibular palpus 

 has 2 setae (fig. 15). There are 9 setae on the 

 distal segment of the endopod and 1 seta on the 

 proximal segment. The exopod has a total of 

 6 setae. 



The first maxilla (fig. 16) has the following 

 number of setae: 11 on the first inner lobe, 2 

 on the second inner lobe, 4 on the third inner 

 lobe, 5 on the second basal segment, 9 on the 

 endopod, 8 on the exopod and 9 on the external 

 lobe. Two groups of small spines are present 

 on the surface of the endopod. 



The terminal part of the second maxilla (fig. 

 17) has 1 enlarged sensory organ, 4 smaller 

 sensory organs and 3 worm-like appendages. 



The first and second basal segments of the 

 maxilliped have 7 and 5 setae, respectively. The 

 r, endopodal segments have the following num- 

 ber of setae: 4, 4, 3, 3 (plus 1 external seta), 

 and 4. 



The first pair of feet have 3-segmented exo- 

 pods and 1-segmented endopods (fig. 18). The 



