68 ME. T. SCOTT ON ENTOMOSTRACA 



also springs from the 8th and 12th joints, counting from the end. The proportional 

 lengths of the joints are nearly as shown in the formula: — 



34 ■ 8 . 10 . G ■ 11 . 16 . 14 . 15 . 15 . 13 ■ 11 . 16 . 15 ■ 18 . 15 ■ 15 . 17 . 9 ■ 16 ■ 10 . 6 

 12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21' 



The jointing of the proximal half of the antennae was somewhat indistinct and required 

 a high power of the microscope and careful focussing to make out the articulations. 

 The right anterior antenna of the male is 15-jointed, and hinged between the 11th and 

 12th joints; both of these joints are fringed with small teeth on the upper margin, while 

 a moderately stout spine springs from the jiroximal end of the 12th joint (fig. 35) ; the 

 male antennoe are sliorter than those of the female, and are provided with a greater 

 number of plumose setse. The posterior antennae and mouth-organs resemble those of 

 Paracartia spiiiicaudata. The first four pairs of swimming-feet also resemble those of that 

 species. The fifth pair in the female have the apex subtriangular and are each furnished 

 interiorly with an elongate stout spine, serrate on the inner margin of the distal half 

 and exteriorly with a long plumose seta (fig. 31). In the male the fifth pair are com- 

 paratively short and stout, as in Acartia denticornis, Brady ; the proximal joint of each 

 is furnished on the exterior margin with a long plumose seta (fig. 38). Abdomen in the 

 female short, stout, and composed of three segments ; the first is longer than both the 

 other two together, the second is about equal in length to the third ; the posterior margin 

 of the first and second joints is fringed with small teeth. The caudal stylets are some- 

 what longer than the last abdominal segment, and are each provided with six plumose 

 setfB arranged as follows : — one, strongly curved, near the middle of the exterior margin ; 

 one subterminal ; three terminal, tlie middle one being much longer than any of the 

 others ; and one (small) on the lower half and near the inner margin of the stylet. The 

 abdomen in the male is composed of five segments ; the first is rather narrower than the 

 next, and the penultimate one is very short. The stylets are shorter than those of the 

 female, but the number and arrangement of the plumose sette are similar (fig. 34). 



Habitat. Lil^reville, Gaboon River, in a surface gathering collected at midday, January 

 28th. The surface temperature of the water was 83°'l P., and the specific gravity 1'02301. 



This Acartia resembles Acartia denticornis, Brady, in several of its characters, but 

 differs in some important points, especially in the armature and proportional length of 

 the joints of the male right anterior antenna and in the form of the male and female 

 fifth feet and abdomen. 



Subgenus Paracartia, n. subgen. 



Near Acartia, Dana, but differing very markedly in the form of the fifth pair of feet, 

 wliich in the female are each armed with a stout curved spine ; in the male the fifth pair 

 are large and unsymmetrical, that of the left side being about half the length of the 

 right ; the male right antenna has also the joints of the proximal half somewhat tumid, 

 as in Pontella. 



