NORTH ATLANTIC PLANKTON. 81 



11). The second joint of the male is drawn down poste- 

 riorly forming a blunt tooth with minute setae at the apex. 



The two last joints are slightly twisted laterally, the 

 caudal segments, which are about three times as long as 

 broad, being further curved round from the perpen- 

 dicular. The right stylet is considerably larger than the 

 left, and has on the outer side a strong prominent spine 

 more than double the size of that on the other segment. 

 Each segment bears five terminal plumose setae. 



The male is at once recognisable by the posteriorly 

 produced tooth on the second joint of the abdomen and 

 by the caudal stylets. 



A number of specimens, both male and female, were taken 

 in the nets on the 12th August, about the mouth of the 

 St. Lawrence, near the Island of Anticosti, and the species 

 was subsequently found plentifully in the plankton 

 collected by Prof. Herdman in Puget Sound, on the 

 Pacific Coast. 



Acartia forcipata, n. sp. (PI. VII., figs. 3 — 10.) 



Length (exclusive of tail setae), 2*35 mm. Body (fig. 3) 

 similar in shape and appearance to the other members of 

 the genus Acartia. Outer branch of posterior antennae 

 (fig. 4) 2-jointed; inner branch 3-jointed, the apical and 

 penultimate joints being very short. Terminations of 

 both joints bear a large number of long setae ; the basal 

 joint of outer branch has seven spinous setae on outer 

 side. Mandible palp (fig. 5) has two short branches, 1- 

 and 4-jointed respectively, both with long setae, some of 

 them plumose. Anterior foot jaw (fig. 6) 3-jointed, bearing 

 numerous long uncinate and plumose setae. Posterior 

 foot jaw (fig. 7) composed of broad basal portion bearing 

 long setae, and a spinous 3-jointed branch. 



Swimming feet, 1st to 4th pair (figs. 8 and 9) 2-jointed 



