frontal margin to the base of the genital segment. The genital segment is distinctly shorter 

 than the combined lengfth of the second and third segments. Vievved from above, the segment 

 appears much dilated in the anterior region. In side view the dorsal line is nearly straight. 

 The ventral surface is much inflated. It is furnished with a well defined tooth-like process at 

 the proximal end. There are no spines at the genital opening as in P seudodiaptomus aurivillii. 

 The second, third and fourth segments are subequal in length. The furcal joints exceed the 

 combined length of the third and fourth abdominal segments. The joints are asymmetrical. The 

 right joint is distinctly narrower than the left. The posterior margin of the first, second and 

 third segments is fringed with fine spines. 



The antennules are composed of twenty-one joints and extend to the end of the third 

 abdominal segment. 



The antennae, mandibles, maxillae and maxillipedes are somewhat similar to those of 

 P seudodiaptomus serricaudatus (T. Scott). 



The four pairs of swimming feet also resemble those of that species. 



The exopodite of the fifth pair of feet is three-jointed. It approaches the shape of that 

 of P seudodiaptomus salinus and P seudodiaptomus serricaudatus, but the internal distal projection 

 of the second joint is nearly as long as the claw-like joint. The second joint of the basiopodite 

 is produced internally, and bears two small spines which may indicate a rudimentary endopodite 

 (Plate XXXVII, fig. 5). 



Male — length 1,52 mm. 



The male resembles the female except, that the right antennule is modified for grasping, 

 the abdomen is composed of five segments, and the furcal joints are shorter than in the female. 



The right antennule is composed of nineteen joints. The seventh joint is incompletely 

 separated. The eleventh, twelfth, thirteenth and fourteenth joints are swollen. The hinge is 

 situated between the sixteenth and seventeenth joints. 



The antennae, mandibles, maxillae and maxillipedes are similar to those of the female. 



The four pairs of swimming feet are also similar to those of the female. 



The endopodite is entirely absent in the fifth pair of feet. The apical joint of the exo- 

 podite of the right foot is in the form of a long sickle shaped claw-like spine. The apical joint 

 of the exopodite ot the left foot is subcircular in outline and lamelliform. The apex is very 

 broad and bears two small spines. The middle of the outer margin is furnished with one strong 

 spine (Plate XXXVII, fig. 8). 



P seudodiaptomus clevei is easily separated from the other members of the genus, by the 

 presence of two dorsal spines on the last thoracic segment, in addition to the strong posterio- 

 lateral spines, and by the structure of the fifth pair of feet of the two sexes. 



Occurrence. — Two females and two males were found in the plankton collected 

 at Station 16. 



This species is dedicated to the memory of the late Professor P. T. Cleve whose 

 researches amongst the oceanic plankton organisms are of the greatest value. 



"7 



