420 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



broad, the ultimate slender, more than twice as long as broad, and 

 originating on the under terminal half of the penultimate segment. 

 The setae shorter than the limb, mostly spine-like and bent. 



Second antenna 4-segmented, segments 3 and 4 united, and flagellum 

 always well developed in both sexes. Mandible with short, strong, 

 mandibular process and 4-segmented palp; its penultimate segment 

 much broadened beyond the middle, its dorsal edge forming a plain 

 blunt angle, at which the dorsal seta group originates (fig. 4). The 

 terminal segment short, thick, little, or very little, longer than its 

 breadth at base. 



Maxilla of typical structure, thickset, maxillary process and palp 

 with short strong bristles; respiratory plate without mouthwardly 

 directed or abnormal rays. 



First to third pairs of legs moderately elongate, their first segments 

 with one seta on the anterior and posterior edges (without knee-seta). 



Furca of female formed of a small basal part with two bristles. 



G. W. Miiller divides the genus into two groups : 



(1) Those with females with shells of length less than once the 

 height. 



(2) Those with females with shells of length more than once the 

 height. 



All species show a plainly apparent yellowish color, formed be- 

 cause of a pale yellow color of the entire shell and from pigment 

 spots in the body. 



Dahl " mentions as of generic worth that the penultimate seg- 

 ment of the first antenna is many times as thick as the terminal 

 segment and all locomotor appendages of a yellowish color. This is 

 also true, at least, of the genera Cythcridea and Gythereis. 



24. CYTHERE AMERICANA, new species. 



Plate LX, flgs. 1-0. 



Dimension*. — Length, 1.2 mm. ; height, O.GG mm. ; breadth, 0.04 mm. 



Seen from the side (fig. 1), the shell is about 1.8 times as long as 

 high, both ends evenly rounded, dorsal edge sloping anteriorly a little 

 more rapidly. Ventral edge slightly sinuate, greatest height just 

 back of the middle. 



Seen from above (fig. G), the shell is about one-half as wide as 

 long, pointed anteriorly and broadest at the posterior third, where it 

 i^ about four-sevenths as wide as long; surface of shell covered rather 

 sparsely with small papillar elevations. 



The preserved specimens as seen by reflected light appear of a por- 

 celain color, covered with a few papillar elevations and not sculp- 

 tured, as is the case with the great majority of the Cytheridse. 



Zool. Jabrb., Abtb. System, Geogr. v. Biol, der Tbiere., 1S88, p. 603. 



