IPHIYLXjOIPOID^. 
LIMNADIAD.^. 
ESTHERIA, Ruppell. 1857. 
Estheria pulex. 
PLATE XXXV, FIGS. 10,11. 
Jlsthena pulex, Clarke. Amer. Jour. Science, Third Series, vol. xxiii, p. 476, plate 0, fig. 4. 1882. 
Esthena ptdex, Packard. Monogr. North Amer. Phyllopod Crust., p. 355; Twelfth Ann. Kept. U. S. Geol. 
Surv. 1883. 
Esthm'ia pulex, Etheridge, Woodward and Jokes. Fifth Kept. Committee on Fossil Phyllojioda of the 
PaliEOzoic Rocks, p. 10. 1887. 
Carapace minute; outline sub-circular; beaks slightly anterior, prominent and 
somewhat incurved. Surface evenly and strongly convex, the most elevated 
point being the center of the valve. 
Hinge-line short and somewhat obscured by the anterior and posterior 
slope from the beak. The surface bears six or eight concentric ridges, 
which are broad and flattened above and separated by narrow furrows. 
The test is tenuous, and the very narrow, impressed interstitial furrows do 
not show any trace of the fine sculpturing often observed in other species 
of this genus. 
Of this species six individuals have been observed, the average dimensions 
of which are \ mm. in length and -f mm. in width. Five of these occur 
together upon a small fragment of shale about 15 mm. square, upon which 
twenty individuals of Entomis, Beyrichia and Leperditia are crowded. The 
specimens are from a thin layer in the Hamilton shales, which is extremely 
