976 PROCEEDINGS OF THE NATIONAL MUSEUM. 



Shell with flang-e-lik(^ projoctions, l3oth anteriorly and posteriori}-. 

 Swiniiuino- settc nioderateh' long. jSIaxillarv process with three strong 

 spines. Second segment of tirst foot with two setsi? on anterior margin. 



Fiirca commonly normal, toothed on central margin. This genus 

 is at onc(^ distinguished by the presence of two setw on anterior mar- 

 gin of second segment of tirst foot, instead of one, as in other fresh- 

 water Ostracoda. Genus established ])v Saussure in 1S58, with the 

 peculiar flange-like projections on the shell as the basis of distinction 



(I Furca about 24 times as long as wide, its dorsal margin faintly toothed for one- 

 lialf its length; shell broadly oval from above mexicana Sharpe. 



na Furca about 18 times as long as wide, its dorsal margin faintly ciliate its entire 

 length. Shell wedge shaped anteriorly from above azteca Saussure. 



I. CHLAMYDOTHECA MEXICANA, new species. 

 Plate J>XIV, figs. 1-6. 



Length, 2.75 nun.: breadth, 1.60 nnn.: height, 1.55 mm. 



Color noticea])ly l)rownish ycdlow, two narrow, greenish stripes 

 rumiing from the lower posterior margin diagonall}' toward the ante- 

 rior upper margin, passing on either side of the muscle impressions 

 and terminating a short distance be^-ond them (tig. 1). 



Surface of shell comparatively smooth, but with a few ver}' short, 

 sparsely scattered papilhe. 



Seen from the side (tig. 1) the shell is highest at the middle and 

 posterior third, sloping abruptl}- to the posterior lower angle, which 

 is provided with a very noticeable hyaline flange. Seen from above 

 (tig. 2) the shell is w-idest in the middle, rather broadh' ov-al, evenly 

 rounded posteriorly, and rather acutely pointed anteriorly. The ante- 

 rior extremit}^ has a verj^ broad, strikingly noticeable flange, fringed 

 with rather long hairs. 



Ventral margin nearly straight, except for a sinus at its union with 

 the anterior flange (fig. 1). 



Natator}- setfe of the second anteimte are very plumose, reaching 

 about to tips of terminal claws. Terminal claws slightly curved, the 

 longest about six times as long as the terminal segment, or seven- 

 fifths as long as the last two segments, the shorter claw two-thirds 

 the length of the longer. 



The "sense club" is quite near the base of the segment on which it 

 is located. 



The second segment of the first pair of feet is provided with two 

 setas, a feature characteristic of the genus (fig. 3). Terminal claw^ 

 stout, nearly smooth, and a})out seven-ninths as long as the last four 

 segments taken togeth(M'. 



The second foot ends in a beak-shaped segment; the terminal claw 

 very nuich ])ent and nearly smooth (fig. -1). The longer seta is about 

 three-fifths the length of the peiudtimate segment, or twice jxs long- 

 as the terminal claw. 



