888 THE AMERICAN NATURALIST. 
III. DARWINULID&. 
Darwinula Brady and Robertson, 1870. 
Shell smooth, thin, and fragile. First antenne short, stout, five- or six- 
jointed, strongly armed with stout, short seta. Second antenna stout, 
composed of four or five joints, no natatory sete, no poison gland or urti- 
cating sete. . Mandible palp three-jointed, the basal joint large and densely 
setiferous. First maxilla bears a large branchial plate; the second a small 
branchial plate and a pediform palp. Post-abdominal rami subconical, 
small. 
a. First antennae composed of six joints, the second antenne of four. 
Antepenultimate joint of the second antenna does not bear a con- 
spicuous one-jointed appendage. Length 0.8 mm. 
D. stevensoni Brady and Robertson * 
aa. First antennz composed of five joints, the second of five. Ante- 
penultimate joint of the second antenna bears a conspicuous one- 
jointed appendage, which terminates in one long and one short 
filament. Length 0.68 mm. to 0.70 mm. D. improvisa Turner 
