Vidria is a genus of proetid trilobites belonging to the family Phillipsiidae. Vidria vespa fossils are found in Middle Permian-aged marine strata of Western Texas. It is unique among Permian-aged trilobites in having a posterior spine emanating from the pygidium of the adult (two such posterior spines are present in immature individuals).Weller, J. Marvin. "Permian trilobite genera." Journal of Paleontology (1944): 320-327.
References
Proetida fact sheet