36 PROCEEDINGS OF THE NATIOISTAL MUSEUM vol. 82 



thirds the length of the inner border and a long slender spine at the 

 outer distal angle. The terminal hook is falciform about as long 

 as the exopod; there is a small spine on the inner border. The 

 first segment of the basipod of the left foot has fine spines on its 

 inner border. The second segment is longer than the corresponding 

 segment of the right foot and has hairs on its inner border.' The 

 exopod is 3-segmented. The first segment is broader than long, 

 has an acute spine at the inner distal angle, and a short, stout, curved 

 spine at the outer distal angle. The second segment of the exopod 

 is short, armed with spines on its distal margin. The third segment 

 IS oval, as long as the rest of the left foot ; it has a single acute spine 

 at its distal end. 



Length: Dahl, female: 1 mm; male: 0.9 mm. Wright, female: 

 1.17 mm; male: 1 mm. 



Occurrence. — Found in the mouth of the Amazon and as far up 

 the river as Santarem. 



Remarks. — Dahl figured a spine by the first antennae of the female, 

 and Giesbrecht and Schmeil use this as a distinguishing character- 

 istic of the genus. Wright stated that " the head bears a pointed 

 process on either side." These spines were not seen in the material 

 studied by the author, but it was noticed that the head has a bifid 

 rostrum. 



The form of the terminal segment of the left foot of the male is 

 peculiar and appears in only one other species, P. clevei. It should 

 be noticed, too, that the figure published here shows three segments 

 in the left exopod of the male fifth foot. In Giesbrecht and 

 Schmeil's synopsis it was stated that the exopods of the male fifth 

 feet are ^-segmented. Though Wright considered the left exopod 

 2-segmented, his figure apparently shows three segments. This is 

 the only species in which this exopod consists of three segments. 



PSEUDODIAPTOMUS HESSEI (Mrazek) 



Plate 19, Figuees 1, 2 



ScTimackeria Jiessei MBi^EK, 1894, pp. 1-3, figs, 1-3. 

 Pseudodiaptomus hessei Giesbeecht and Schmeil, 1898, p. 65. 



Female. — The last thoracic segment is rounded. The distal bor- 

 ders of the first three abdominal segments are armed with spines. 

 The furcal rami are about three times as long as wide. The third 

 f ureal seta is broader than the others. The first antennae have 22 seg- 

 ments. In the fifth foot (pi. 19, fig. 1) there is a hyaline projection 

 on the second segment of the basipod; the second segment of the exo- 

 pod has a small acute spine at the outer distal angle, a large plu- 



