We present an elemental abundance analysis for four newly discovered ultra metal-poor stars from the Hamburg/ESO survey , with \mathrm { [ Fe / H ] } \leq - 4 .
Based on high-resolution , high signal-to-noise spectra , we derive abundances for 17 elements in the range from Li to Ba .
Three of the four stars exhibit moderate to large over-abundances of carbon , but have no enhancements in their neutron-capture elements .
The most metal-poor star in the sample , HE 0233 - 0343 ( \mathrm { [ Fe / H ] } = -4.68 ) , is a subgiant with a carbon enhancement of \mathrm { [ C / Fe ] } = +3.5 , slightly above the carbon-enhancement plateau suggested by Spite et al .
No carbon is detected in the spectrum of the fourth star , but the quality of its spectrum only allows for the determination of an upper limit on the carbon abundance ratio of \mathrm { [ C / Fe ] } < +1.7 .
We detect lithium in the spectra of two of the carbon-enhanced stars , including HE 0233 - 0343 .
Both stars with Li detections are Li-depleted , with respect to the Li plateau for metal-poor dwarfs found by Spite & Spite .
This suggests that whatever site ( s ) produced C either do not completely destroy lithium , or that Li has been astrated by early-generation stars and mixed with primordial Li in the gas that formed the stars observed at present .
The derived abundances for the \alpha -elements and iron-peak elements of the four stars are similar to those found in previous large samples of extremely and ultra metal-poor stars .
Finally , a large spread is found in the abundances of Sr and Ba for these stars , possibly influenced by enrichment from fast rotating stars in the early universe .